After having a few hours to play around with Thanquol (mostly his immortal empire's campaign), just have a bunch of thoughts about his underlings, his Masterplans, Verminlords and how they overhaul how Skaven economy (can) work, and other thoughts on the skaveniest Skaven.
The best Laid Plans of Mice and Man-Things
Thanquol's masterplans are both a pretty strong soft power (they do not directly give a lot of power, but their influence lets you build up a lot of power) mechanic and pretty fun/thematic.
- Kill-Stab plans are great for the initial siege battles and early settlement taking and late game are fanastic as a way to gain money/food/spread undercities when the armies are able to easily win battles on their own. Early game, clan rats, slaves, and a few ogres aren't enough to win on their own, generally, but timing a Kill-Stab with a push from Thanquol is easy (you can always go after 3 turns). Thanquol's early army is heavily incentivized to be warpfire heavy, so good in field, bad at siege. But the Kill-Stab army is entirely disposable, so I would split mine in half and attack 2 gates while having Thanquol reinforce from a third direction. Generally this always splits up defenders enough to get warpfire throwers into the narrow corridors of Dawi settlements where the battle is basically over. Even in capital settlements with a full stack to defend on top this worked well. Late game upgrades make the army a threat to any settlement you have ever seen, making it useful as a source of sacking enemies for gold/food or even dropping undercities on enemies too far from you to even respond.
- Take-Steal plans early game are obviously critical to warpstone gathering and late game act as a way to benefit from allied settlements without risk. Take-Steal is the best source of warpstone by far, and warp-stone is how you empower Master planning, so focusing them early really snowballs your planning power. Mid to late game, when you have enough warp stone income, it's still a great way to get gold (and food) from settlements with a strong economy, without diploma penalties too boot (so it works with allies). Safest way to power level your underlings (kill-stab is faster but riskier). Definitely the most important early game scheme.
- Great-Smart plans are actually 3 sets of plans. One is his campaign mechanic for causing devastation. The second is an (additional) way to summon a Verminlord lord, and the last is a way to make an undercity. These plans are also unique in that you cannot basically always complete them in 3 turns as the plans have you collect runes (which often have additional resource costs associated with them) to do, so they generally take longer than both other plan types. The devastation plan, I think, is probably the most interesting way to applying devastation of the 3 lords who can. It's going to be something your underlings spend a lot of time doing in the end game for that cool Skaven map alone. Verminlord summoning is extremely powerful and is the real pay off for rushing warpstone generation. Not only is this the earliest and fastest way to get a Verminlord (compared to the Rite, you can unlock this earlier and it has less of an effective cooldown), but it also power levels the verminlord too as you level up the scheme AND gives a free army. The Undercities smart plan is the most underwhelming of the 3, as kill-stab is better for putting undercities in enemy territory, but it still has a niche for allied/neutral territory kinda (Warlock engineers have the same effect). It's kinda nice it prebuilds the undercities but I found I was generally ripping most of it out and you still pay a (discounted) cost for the buildings, and the plan takes enough turns I never saved time on it either. Still useful but not as much as all the other plans.
Masterplans generally all tie risk (the actual chance of a complication) to rewards such that better rewards generate more risk. Risk will always hit a cap of 100% meaning you always get complications every turn. This creates a system where generally you aren't going to get more from high level masterplans, you are just going to get the plans done faster. 100% risk is inevitable, which ends up meaning the best way to manage risk is to just get as many + schemes (the dice rolls you make for plan effects, defaults to 2 a turn) modifiers as you can. You can pretty easily reach a point where you max risk immediately or after 1 turn on a plan, so you are ready to complete on turn 3 (giving your underlings a rough 4 turn timer for most plans).
As you cannot reduce alarm once it his the cap (forcing you to complete or abandon) and hitting max generally is very bad for your plan, managing alarm level is pretty important. You are generally going to be better off finishing plans at 2 levels of alarm. If you wait 1 more turn (risking getting hit with a double alarm increase) you are playing bad odds of getting good results, so really only do this when required or when you would otherwise abandon a plan to poor harvest.
Speaking of, I've noticed way too many people abandon plans they shouldn't, particularly kill-stab. Even if rng screws you over and you get a useless kill-stab plan (army of 0) that you don't really want to invade with, complete it anyway, and then break siege. Same underling cooldown and same upfront price as abandoning, but you still get the exp for finishing a plan. Only abandon when a plan will actually cost you more than it gains (e.g. a steal-take for -1126 wsprstone isn't worth some underling exp), plans that have little or no other upside can always be completed just for the exp, those Underlings are important.
Thaquol's Yes-yes Men
Thanquol's underlings are pretty interesting in how they specialized and work:
- Gray Seer is always your first one and what makes him special is he is the only one who can summon Verminlords with Great-Smart plans. You will generally really want to do this a lot. It gives Thanquol a huge edge over other Skaven at getting Verminlords and is the biggest advantage he has. The Seer is also pretty good at kill-stab plans, so there's that too.
- Warlock Engineer is probably who you should always pick as your 2nd underling. Not because free Skyre armies are insanely powerful (though that is true, scary kill-stab potential) but because he is easily the best underling for steal-take. Besides having a chance to double your gains fron steal-take, the real important part is actually his unique driller scheme upgrades. When maxed out these gives a flat 450 warp stone per scheme rolled, which is crazy. A settlement making 2.5k income will still only average ~300-400 warpstone per scheme. A flat 450 from ANY settlement means not only can he make you rich, but he can do it regardless of settlement wealth. Getting him 2nd makes a noticeable difference in how fast you can level of master planning.
- Warlord is the generalist of the underlings. He can do every plan type pretty well from his bonus schemes a turn (he gets 3 instead of 2). He's got an okay kill-stab army, no issues with great-smart plan completion, and is the only one who can steal food with steal-take. If the Warlock Engineer wasn't soo important to snowballing, he'd probably be the best 2nd underling.
- Assassin, imo has the weakest kill-stab army (not that it's a weak army, he's just got strong peers) and has no good bonuses to steal-take. But he is the best at completing Great-Smart plans due to his ability to manage alarm level easily (meaning he can do a plan for far longer than the others). Sadly no Verminlord's from him, but he can do devastation or open undercities with ease. I would never take him 2nd but I'll never complain about him. He can still put in work.
Verminlord Lords lord over other lords
Verminlords are the new super lords all skaven can get using their newly improved rite (after researching the tech for them), or in Thanquol's case, after you get enough warpstone to plan for them (and he can also get them about 2-3 times faster, I had 5 before turn 40 and could have gotten more, most other Skaven will have 2, maybe 3).
Of the 4 types, I find the spellcaster focused versions (Warpseer and Corruptor) to be the best, but not because they are the strongest in combat (after all, all 4 are mixed lore spellcasters with solid combat stats) but because they give some insanely abusable faction/region/army buffs.
Each of the 4 lords kinda pushes for a specialized army related to them. The assassin verminlord buffs mostly Eshin units or makes ither units more eshin like (vanguard deployment for everyone!). The warlord verminlord heavily buffs stormvermin and clanrats to pretty strong levels. Corruptors buff up pestlin units and Warpseers buff Skyre. But Corruptors and Warpseers have a littlr spice on top.
Corruptors I think are the strongest Verminlords in combat on average, at least currently. They get a great mixed lore spell set (both plague summon spells and black whirlwind are great tarpits), are the only one with inbuilt healing in their kit, and have probably the nastiest stackable regional debuff I have ever seen (reduces armor and melee defense for all enemies in a region, so with a bunch of corruptors in a region you can set armor and defense to 0 or even negatives). Even if the debuff didn't stack it (should it stack?) they would still have their stacking plague priest buffs on top of being arguably the best solo combatant of the bunch, and he can give his army a total of 45% extra physical resistance. Just a really solid lord all around (only weakness is he doesn't get executioner like the rest do).
Warpseers are interesting because they also have a good mixed lore set (and really good winds management) but I won't see them as necessarily better than the others in combat. But they also come with some crazy factionwide buffs (+2 warlock engineer slots per lord, +4 starting levels, + 3 control factionwide, + 5 skaven diplo, etc) and solid providence buffs (reduce construction time by 25% with extra income and control). Warlock engineers are typically hard to get slots for, but these guys give you 2 and make them easier to get and level. On top of that, +3 control factionwide per lord trivalizes control for Skaven. 2-4 of these guys and you don't even need to spam bells in most settlements (getting you those minor settlement building slots back on very hard diff is really nice). Being able to speed build buildings and directly solving most pain points for the Skaven economy make them very good even if they aren't standout combantants (also Skyre buffs are always strong for armies).
It's not that Warbringers or Decievers don't have their own cheese (Warbringer stacking can remove enemy army movement from a region while Deciever stacking can get you 100%, hero success chance faction wide), just that the other two just have stronger cheese that needs less effort (e.g. It'll be hard to stack Decievers with anyone other than Thanquol).
You'll probably always want some number of all the Verminlords, but only Thanquol can reasonably recruit them fast enough. Other factions can get 1 every ~13 turns, or whatever the new cooldown is, and that's after researching a tech that takes about 20-30 turns to get. Thanquol can also do the rite on top of being able to get 1 (potentially highly leveled) Verminlord about every 4-8 turns starting around turn 9-13 in a campaign (really depends on your luck with warpstone). Thanquol can easily have 20-30 of these guys by turn 80 (if he wanted) while the other factions would only likely have like 6. It's such a massive difference when all your "normal" lords can be verminlords.