Corrosive Mentor {2}{B}
Creature — Elemental Rogue
Black creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.)
click a line to search just that ability, click more to combine them
Cards that do something similar expected a card that isn't here?
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.