Weapon choices for the Hekaton Land Fortress in the 10th index

 Time has come to look at the weapons that can be taken for the Hekaton Land Fortress in the Leagues of Votann Index for 10th edition 40k.

The Hekaton Land Fortress is the natural centerpiece of a League of Votann army, being both the largest and the toughest model available to us. At slightly less than twice the cost (in points) of of a Sagitaur, it has toughness 12, 2+ save and 16 wounds. As it is remarkably easy to get cover with this model in 10th edition, it usually has fairly little trouble surviving until the later stages of the game.

With a transport capacity of 12, a speed of 10", OC 5 and the ability to buff a shooting unit that leaves its  confines, the Hekaton can be a strong punch into enemy lines. But what about its guns? It has several options. Which one is the strongest? Let us first see what options we have. For the Hekaton, we have three sets of choices to make, in addition to a mandatory MATR Autocannon.

Choice 1: Sponson guns

The Hekaton Land Fortress has four sponson hardpoints, that Games Workshop has chosen to model as two twin-linked weapons options. Thus, you get either two Twin Bolt Cannons, two Twin Ion Beamers or one of each.

We know the Twin Bolt Cannon from our analysis of the Sagitaur, where we concluded that the combination of an excellent (for Votann) 36" range and its other stats means that it's a reliable way of putting a wound on almost any kind of target.

The Twin Ion Beamer however, is shorter ranged at only 18". Higher strength and a point better AP than the twin bolt cannon, along with a better sustain value means they look better - but each hit only does 1 damage, where the twin bolt cannon does 2. This is going to be an interesting comparison. 

Before calculating anything, my money is on the Twin Bolt Cannon in this matchup, but I think it'll be close.

Choice 2: Main gun

There are three options for main gun:

• The Cyclic Ion Cannon is the anti-horde choice among the guns. It has the Blast keyword and an impressive D6+3 attacks, it is clearly meant to target as large units as possible. But strength 9, AP-2 and 2 damage per shot means that this gun might be able to punch up meaningfully into harder targets.
• The Heavy Magna-rail cannon is the heavy hitter. The heavy keyword means it can hit on 3s even without a token on its target, and it has a range advantage over the other main guns at 30" vs their 24". At only one shot, the rail cannon will whiff fairly often, but when it does hit it is dangerous: Strength 18, AP-4 and D6+6 damage is scary enough, but this gun also causes Devastating Wounds. Sadly there's no good way of improving the chance of that happening. The Heavy Magna-rail cannon is notable for being the only AP-4 weapon in the Votann index.
• The SP Heavy Conversion Beamer seems the middle ground, having 2 shots and Sustained hits D3, strength 10, AP-2 and 4 damage per shot - as well as the conversion special rule that lets it score critical hits on 4+ at ranges between 12" and 24". I'm a bit sceptical to the value of conversion beamers after reviewing the infantry variant, but the stats are different so maybe I'll be surprised.

Before calculations, my money is on the Heavy Magna-rail cannon in this group. My experiences with it shows that it usually takes out one or two heavy targets per game, but it does swing a lot. In a recent game against the Necrons, it took the gun 4 turns of shooting at a Doomsday Ark before it did anything of note, but when it did do something it basically killed it in a single shot. (It was the shot of a century and involved the Ancestral Sentence stratagem and three natural sixes rolled in a row.) Beyond its damage potential, I like the 30" range.

Choice 3: Pan Spectral Scanner vs Hekaton Warhead

Finally, we have the choice of taking a Pan Spectral Scanner, which lets every other gun ignore cover (which is amazing in 10th edition), or a Hekaton Warhead - a one-shot indirect blast weapon with D6+3 shots, strength 7, AP-2 and 2 damage.

I'm generally wary of one-shot weapons, and though the Hekaton Warhead isn't bad for that kind of weapon - the amount of shots means it's fairly likely to do something close to its average output - I'm really expecting ignoring cover for every gun for the entire game to be better. If this choice was on a Sagitaur, it would be a more serious competition as Sagitaurs tend to die in a couple of rounds. But in my experience Hekatons stick around for several rounds. I have yet to field one without getting to shoot at least 3 times. So before calculations, I'm thinking the scanner is the way to go. But we'll see.

Base case

Without any buffs or debuffs, things look like this.

The guns seem to be fairly well balanced. For the sponson guns, the Twin Bolt Cannon is in the lead for my priorities, its damage characteristic of 2 beating the Ion beamer in most categories. To be fair, the beamer isn't far behind at all - but the fact that they are this close mean that 36" range vs 18" wins the day.

For main gun, the surprises are starting for me. That the Cyclic Ion Cannon is the best at killing light and medium infantry is no surprise at all. But I had expected the Magna-rail cannon to do better. Instead, we see that even a low invulnerable save on the target means it doesn't do significantly better than the conversion beamer at short range. The only place it does beat the heavy conversion beamer by a significant margin is against the T12, 3+ target without an invulnerable save. It should be noted that T9-12 targets without invulnerable saves are a lot more common than our choice of target profiles may lead you to believe. But then we look at what the Conversion beamer does at long or conversion range, and things aren't looking too good for the Magna-rail.

The Magna-rail does still have a range advantage, which can be significant. But the wider spread of good options for the SP Heavy Conversion Beamer probably evens that out. It is also much more dangerous in overwatch, due to its sustained hits rule.

Cover and the Hekaton Warhead

Lets get this out of the way: Without the Hekaton Warhead, we're going to lose efficiency whenever we fire into cover. This is what the guns do against targets in cover:

Cover is "everywhere" in 10th edition, so the damage from the Hekaton Warhead has to be enough to make up for that loss. Here's the loss in efficiency, along with some calculations for the Hekaton that I'll explain in a moment:

In my experience, a Land Fortress gets to shoot 3 or 4 times in a game. Lets say that out of those, it's firing at enemies in cover 2 times. This means the Hekaton Warhead needs to do more damage than 2 times the difference to be worth it. (Technically it could do less if firing it early meant taking out a significant target, but it doesn't do damage enough to make that likely.)

In the "Loss with TBC and Rail" column, we see the total loss of efficiency to cover on a Hekaton firing into cover once with all its guns, assuming it chose Twin Bolt Cannons and a Heavy Magna-rail Cannon. Note that these are choices favoring the Hekaton Warhead, as they lose comparatively little by firing into cover - especially the Magna-rail.

Even with these fairly conservative assumtions, the Hekaton warhead never does more damage than what you lose from 2 rounds of shooting into cover, against any sort of target. In many cases it does less than a single round of shooting into cover would lose you, though it becomes close in that case.

I'm not sure what GW was thinking with the balance of this choice. Maybe it was balanced against 9th edition terrain rules, where cover was far less common. Or mabye the playtesters got much better than I've been at preventing the enemy from getting cover by moving smartly. For now, just pick the Pan-spectral Scanner and move on.

Tokens

What happens when we get one or two tokens onto the target? We're assuming no cover due to a Pan-spectral Scanner in all these cases.

The tokens don't seem to change much in our matchup. The Twin Ion Beamers don't pull ahead, at least not enough to justify the range difference, so the Twin Bolt Cannon still rules supreme in the sponsons.

For the main gun, the Heavy Magna-rail Cannon falls behind more than I would have thought, only being the best in range (at 30" vs 24" of the alternatives) and against very tough targets without invulnerable saves at ranges closer than 12"). The Cyclic Ion Cannon is supreme at killing infantry, including heavy infantry. The SP Heavy Conversion Beamer in conversion range is the best at killing heavier targets.

The likelyhood of being in conversion range

If the Conversion Beamer isn't in conversion range, things change quite a lot - especially before you get that second judgement token on the target. The Magna-rail cannon then looks a lot better. In the games I've played of 10th this far, the Land Fortress has at some point ended up at point blank range. But generally this happens in the last rounds of the game.

Having the Conversion Beamer might mean the enemy tries to close that gap sooner. In which case you should have a plan to deal with that. A possibility is having Hearthguard or Beserks in the Land fortress or otherwise nearby as a melee threat, to make the enemy want to stay away. This may or may not work. Of course, if you have melee troops in your Hekaton you probably want to advance close to the enemy, so this can be self-defeating.

The way I've been playing, with a single Hekaton following up behind, or flanking, an advancing screen of Sagitaurs and Pioneers, I'm thinking the SP Conversion Beamer is looking very tasty, even if it might not be optimal in those latter rounds of the game.

Overwatch and degrading

I won't force you to read another table, but lets consider overwatch for a moment. The Twin Ion Beamer and the SP Heavy Conversion Beamers have clear advantages here, both having Sustained D3 meaning that any 6s to hit will do D3+1 hits. For the Twin Ion Beamer, I still don't think this outweighs the range and damage advantage of the Twin Bolt Cannon, especially as that gun is still Sustained 1 - so the difference isn't that great. For the SP Heavy Conversion Beamers, however, it is significant - they are already the best option in a lot of cases, and this is another case in their favor.

The other guns can benefit from the Ancestral Sentence stratagem - I did have that great moment of doing 3 hits with a Heavy Magna-rail cannon due to that stratagem the other day, but it's not exactly something you want to rely upon happening. And any stratagem you don't have to spend CP on is great.

Degrading by taking damage down to 5 wounds or less makes the Hekaton Land Fortress worse at hitting. This favors the same weapons as Overwatch does, those that have the Sustain rule. Another point for the SP Conversion Beamer, and a small one for the Twin Ion Beamer.

Burst damage

In all my articles on weapon choice, I've talked about averages, as I think that is the most useful criteria. And we haven't had that many weapons that could do significant burst damage. But here we do. In 10th edition Warhammer 40k, very few targets degrade significantly or early. So doing a fraction of a targets wound capacity doesn't really hamper your enemy until you've done enough damage to take it out.

It is therefore a lot better to have a chance at doing a lot of damage all at once, to take the target out early, even if averages would say that the target dies a bit later.

The maximum damage of the main guns against a single model (without stratagems) are 18 for the Cyclic Ion Cannon, 12 for the Heavy Magna-rail Cannon and32 for the Heavy SP Conversion Beamer. I'm a bit surprised here, as my intuition tells me the Magna-rail should be the optimal weapon for burst damage. But the damage value alone isn't really what's at stake, what is at stake is the probability of doing enough damage to kill a target.

This calculation will very quickly become very black magic indeed, but lets start with something simple: The probability of doing max damage against our Knight target with no tokens. No tokens is chosen because it isn't always likely that our target early game will have any.

• Cyclic Ion Cannon: 1/6 (the chance of rolling 9 attacks) * (1/2 (hit rate) * 1/3 (wound rate) * 2/3 (save penetration rate)) to the power of 9 (number of shots) =  1/6*(1/9)^9 = 4.3*10^-10... that is 0.00000000043.
• Heavy Magna-rail Cannon: 1/2 (hit rate) * (1/6 (mortal wound rate) + 2/6 (normal wound rate) * 1 (save penetration rate)) * 1/6 (chance of rolling the max number of wounds) = 0.042
• Heavy SP Conversion Beamer (in conversion range): (1/2 (chance of hitting) * 1/3 (chance of rolling full sustain) * 1/3 (wound rate) * 2/3 (save penetration rate)) to the power of 2 (number of shots) = 0.00137

Some rounding here, but the point is that while the maximum damage of Ion Cannons and Conversion Beamers are higher than that of the Rail cannon, getting to that maximum is much harder for them - though the conversion beamer is less far behind than I thought.

But most targets don't have the wounds of a Knight, so you don't need to do max damage, you just need to do enough. How about killing a Rhino? It has T9, Save 3+ and 10 wounds.

Heavy Magna-rail Cannon: 1/2 (hit rate) * (1/6 (mortal wound rate) + 3/6 (normal wound rate) * 1 (save penetration rate)) * 1/2 (chance of rolling 10 or more damage) = 0.1667. This gun will one-shot a Rhino 1 out of 6 times.

Cyclic Ion Cannon: The math here becomes a little bit complex. The minimum number of shots you need is 5, so you have to roll a 2 or better on the number of shots. But each such case needs to be treated differently... this gets a bit ugly to do by hand (and by hand I mean calculator and excel), so I wrote a quick AnyDice program for it. The probability of doing 10 or more damage, as shown by the At Least-tab on AnyDice is 0.01 - so one-shotting a Rhino is a 1-in-a-100. Significantly lower than the Heavy Magna-rail. Of course, this is as expected for the anti-infantry gun, but what about the Heavy SP Conversion Beamer?

Heavy SP Conversion Beamer: This one feels even more complicated than the Cyclic Ion Cannon, so again we write an AnyDice program. As you can see in the graph below, the chance of doing more than 10 damage against a rhino is 0.2778 with full conversion, more than 1-in-4, significantly higher than the Heavy Magna rail. Even without full conversion the chance is still 0.1528, which is lower than one-in-6 but higher than one-in-7 - almost as good as the Magna-rail.

Admittedly, the Rhino is at some pretty sweet break points for the Heavy SP Conversion Beamer for toughness and armor save. The Heavy Magna-rail will do better against the toughest targets for burst damage, at least without full conversion. But the Conversion Beamer will do better against "weaker" targets, as well as targets with invulnerable saves that render the AP-4 of the magna-rail inefficient.

I think the field is closer than the Rhino example makes it look like, but the SP Heavy Conversion Beamer wins this one as well.

Conclusions

Going back to where we started, we have three choices, and I think we have a fairly clear winner for each of them.

Choose the Pan-spectral scanner over the Hekaton Warhead unless you're playing with no terrain at all. Really _no_ terrain. A single round of shooting at a target in cover, and the scanner has very nearly made up for missing the warhead, two rounds and there isn't a contest.

For the Sponson guns, I'm going to strongly recommend the Twin Bolt Cannon. Its output is pretty similar to that of the Twin Ion Beamer as long as the target doesn't have cover (and it won't, as we'll be picking the scanner). The improved performance of the Twin Ion Beamer in overwatch and in other rare conditions such against stealth don't outweigh an 18" range disadvantage for me.

Lastly, for the Main gun, a big surprise for me! I'll have to strongly recommend the SP Heavy Conversion Beamer. While in conversion range, it either outperforms or at least matches the other options against everything from a terminator to a knight, and with tokens it gets even better. If you have to fire at short range it becomes less attractive, but it's still not a bad gun by any measure - much better than I would have expected. It also has very significant burst damage. And the fact that getting a sustained on the main gun will make me stop wanting to spend CP for Ancestral Sentence on the Hekaton is good.

The other two options do get honourable mentions here. The Cyclic Ion Cannon is a very good anti-infantry weapon - up to and including elite infantry such as Gravis and Terminators, but I just feel we have more need in the army for guns that can deal with tough targets. And with it's MATR Autocannon and Twin Bolt Cannons, the Land Fortress has plenty of anti-infantry guns already.

The Heavy Magna-rail cannon is also a good option, giving you a chance of putting serious damage on a hard target without an invulnerable save without the help of judgement tokens. It also has a range advantage. But from the numbers, I think the SP Heavy Conversion Beamer will perform better. I've been running the magna-rail in the games I've played, and I've been happy with it, but it is getting swapped now. Happy I magnetized.

So to summarize: Equip your Hekaton Land Fortress with a Pan-spectral scanner, two sets of Twin Bolt Cannons and a SP Heavy Conversion Beamer.

And that's it for our dive into the calculus of war for this time!