Black Blood of the Earth

As an exiled blood alchemist you'll need to use every resource at your disposal to return home and get revenge.  Be cautious though, the further you travel from the center of your prison dimension the stronger your wardens become. You might be able to access nearby prison dimensions, perhaps they'll have useful resources.

Since your blood is corrupted from your experiments you'll need to get creative to power the blood magic ritual to return home. Since you can't cut yourself to fuel blood magic you'll have to gain life essence from other sources. You've got some ideas on how to increase the efficiency of slate creation as well as sacrifices. A redesign of the coat of arms blood collector should help as well. Luring villagers back to your altar with emeralds might work too.

Join or fight the roaming Vampire packs. Arm yourself with Dwarven weapons. Use witchcraft or divine spirits for magical assistance.