Gloomwrought Stronghold

shadowfell (whenever a swamp enters under your control)
choose up to 2-
all revenants you control have swampwalk
or
you gain control of all undead type creatures (this includes vampires, zombies, ghouls, and any other type of undead using logic as your key to undead)
or
destroy all non revenant creatures they cannot be regenerated (this includes colorless creatures and devoid creatures and ignores indestructible)