I love Moose being a scientist and all but I'm an idiot who knows nothing about biology. He works with and studies the undead though so it's kind of fun coming up with what he does for his research.
Undead typically come in two types: Supernaturally induced, like necromancy summons, mummies animated by ancient curses, ect. And biologically induced, like certain types of zombies, vampires, "frankenstein" type creatures, ect.
There are also varying levels of self-awareness in undead. A zombie animated by a virus will mindlessly try to plow through obstacles to get to a food source. They have no awareness of their surroundings or have any sense of self-preservation. A skeleton, on the other hand, can understand basic commands and even use weapons. And others, like vampires, certain types of zombies, ect are basically still human but dead because they lack all biological signs of life. There's a huge spectrum and a lot of overlap between cause of undead and level of intelligence retained after death.
And what's also interesting is how the undead is present in every corner of the universe. He's worked with everything from mummies in Egypt to vampires in Romania, ghosts in machines to skeletons in space suits, funguses that spread by decaying to animals who are almost nothing but bone.
Every type of undead also has specific containment requirements too. Temperature and moisture levels to preserve their forms, magical forces to ensure longevity of summons, fortified enclosures to account for physical strength. And ones who are fully mentally functional are left to live their lives in society, only needing to check in with the facility now and again for things they need in exchange for being interviewed or getting basic examinations.