Kormus' DoomBone Bell

When Kormus' DoomBone Bell comes into play,
Choose Shade, Spiris, Vampire, or Zombie;
creatures of the chose type get +1/+1.
All Swamps are 1/1 black Skeleton creatures with
"{1}{b}: This creature gains Invulnerability until
the end of the turn.". They are still lands.
Sacrifice a Swamp {t}: All Skeletons gain
Invulnerability until the end of the turn.
"Liliana laughed, zombies were no longer enough!"