A few people seem to be overstating the power of uncroaked troops. If Erf follows the standard game principles, they have drawbacks.

No morale bonuses, (or penalties) period. For most games, morale is as powerful as any other type of bonus, and never getting it at all makes your entire army kind of lukewarm. Also, any living units in the same army will have their morale bonuses destroyed by the allied uncroaked.

Units cannot be healed of damage except by powerful, non-conventional magic. Any units lost cannot be recovered. Ansom the Obedient? After a few battles he will look a little hacked up, unless the turn reset magically applies to uncroaked as well.

They have extra weaknesses to things like fire and holy magic. They have no particular strengths except immunity to things like diseases and mind-spells. (fear)

They cannot follow complex instructions, usually.



Etc. Bottom line is that a tool like the Hammer is drastically more useful in a real strategic situation. It lets you build up a strike force of appropriate size, crush enemies, and collect appropriate resources in the conventional way. The Pliers, on the other hand, require a war already underway, and enough allied troops to actually win the current battle. The pliers do nothing any time the enemy is stronger than you are, because you will lose more of your undead than the enemy will lose living troops.