Ok heres my ideas (taken from reading all the posts)
"Primre" castes:
Lich: Your most powerfull class liches are necromancers ascended into undeadoud? via dark magicks. They are powerfull mages and can raise temp zombies from corpses.
Shade: Your most standard caste the are the souls of the dead taken over by an evill spirit. They are imatirial (verry high doge skill) and can disolve non setntient living mater on touch (great melle hunters and they dont need axes to chop down wood) but are verry physically weak (low hp).
Ctulu... dudes... types...things
: They are the most physicall of the three and the only "prime" caste that can mine. They can derrefy enemys in too fleeing but are desent fighters on ther own.
All of the "Prime" castes have a way of dealing or escaping the enemy, Lichs can raise corpses, Shades can doge, and Tculu's mates can terefy!
And now the part i like... The Constructs!
They undead , as you saw, are fearly weak in combat and other phisical labors so the need a "Slave" caste!
"Slave" Castes:
Abominations: Hulking piles of corpes sewed tougether to create this monstrocity! They gain masive bonuss in combat and are are the hardest too build needing the corpes of 3 sentiend creaters!
Skeletons: Your basic manual laborer the Skeleton gains bonuses in crafting, crapentry and masonry. They are made for bones.
Flesh sacks?: They are the easyest ones too make needing only 10 meat but are not particalry good at anything, but if you need a quick fighting force or just soem menaeal labor the flesh sacks are for you!
All of the "Slave" Catses can mine and craft.