DERP. I'll fix that.
No medal, but here's some exposition as a reward.
So yeah, Zombies get progressively better the more recent the animation and the better quality corpse. A man with a gash in his neck will make a better zombie than the man who's been dead 15 years, but a worse zombie than the man who was poisoned and/or preserved. Skeletons work almost exclusively through magical animation, so Skeletons have a kind of half-mind deal, not unlike an AI. They can think through complicated paths, but they can't problem-solve at all because the gears in their skulls just tell them "move towards target as quickly as possible" and don't factor in the massive dragon-riding Giant with a flamethrower that happens to be standing there. A zombie varies on the problem solving; day of the dead style zombies are Old and Ancient Zombies, while Recent, New and Fresh zombies are closer to the ones from left 4 dead. Pristine zombies can almost blend in with people, albiet as a really dumb person.
Ghouls are more advanced but similar to zombies, but they require trapping a spirit inside the flesh rather than magical reanimation without the spirit being trapped. Becoming a ghoul is painful for the spirit and a rather bad thing to do, but it means ghouls are stronger and smarter than zombies, with problem solving on par with a smallish child. They also don't need preservatives to keep from decaying as the spirit inside can activate parts of the body again. The main way for normal people to deal with ghouls is to whack them with holy water, which breaks the spell binding the spirit inside. The ghouls will do one of two things: Deanimate as the spirit goes back ot whatever afterlife they were in before, or go on a rampage against the necromancer that made them. They're seen as extra evil by normal people and necromancers alike.
Liches are Necromancers who have placed their brain inside a enchanted jar and become what amounts to a really smart skeleton. Like uploading your brain in science fiction, this has quite a few advantages and disadvantages. On one hand, your body is now completely meaningless. A lich can survive being destroyed completely and totally so long as their Souljar remains unbroken, and can evn start froming a new body to inhabit by hitching a ride on a Skeleton or Zombie under their control. They also get really smart, since they now have what amounts to two brains: the magic one inside their body, and their real one in the jar. They can read two books at once, think two thoughts at once, whatever, so long as each brain is capable of it's individual task. Since the body is run by the magibrain, they can also hide for a long time doing absolutely nothing in a small dark place and not go crazy. They just put their main brain in sleepmode and let the magibrain take over.
Ghosts are spirits called from the beyond by a necromancer or traumatizing event. They can be pulled from an afterlife by force or by persuasion, depending on the necromancer. Lenen here probably won't use the forceful route since he's not an ass, but some of the more stereotypical necromancers can and will bind a ghost in chains, and since the ghost isn't corporeal unless it needs to be, you can't hit it with holy water. The only way to free a ghost is by countering the spell magically, and doing that while it's lifting your through the air to drop you ro slashing at your gut or whatever is pretty damn hard. Ghosts are very powerful, with minimum power proportional to a Fresh or Pristine zombie, and maximum power not yet found. Ghosts need powerful magic to keep them here though, and even moreso for the chained ones. For this reason, they're used rarely even my major necromancers, unles they can get ahold of a dragon corpse.
Dragons, like any animal, can be made into whatever the necromancer wishes, besides a Lich (which is possible but utterly insane). A Dragons bones are iron-hard, muscle large and dense enough to crush buildings, and scales like tempered steel. They also have strong, rebellious souls, one of the resaons not to make a Dracolich, and also why a ghostly dragon is a terrifying sight. Part of the fear comes from the idea you'll have to fight a twelve-ton semi-visible ultra-strong behemoth, and part of it from the idea you'll also have to fight the guy behind it. Dragons are rare however, and most don't like being raised from the dead, since it implies servitude. They are very, very dangerous.