Each other creature you control that's a Zombie or Mutant gets +X/+X, where X is the number of counters on Hancock.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
Reports become test cases the matcher is graded against before an update ships.
Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math,
and examples like yours decide which differences should count.
Vault 12: The Necropolis88%
$0.47↓#66790.122.6 years
"Put two +1/+1 counters on each creature you control that's a Zombie or Mutant."