For the necromancer barons, killing and recruitment are one and the same.

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Foundations

Midnight Hunt Commander

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch.

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Core Set 2019

A creature that's both a Skeleton and a Zombie will get the bonus only once.

Because damage remains marked on a creature until it's removed as the turn ends, nonlethal damage dealt to a Skeleton or Zombie you control may become lethal if Death Baron leaves the battlefield during that turn.

Death Baron doesn't normally affect itself. If you manage to turn it into a Skeleton, however, then it will give itself +1/+1 and deathtouch.