Delta Bloodflies

• WWizards of the Coast2025-04-04
  Official Ruling
  Delta Bloodflies’s last ability checks at the moment it would trigger to see if you control a creature with a counter on it. If you don’t, the ability won’t trigger at all. If it does trigger, the ability will check again as it tries to resolve. If you don’t control a creature with a counter on it at that time, the ability won’t resolve and none of its effects will happen.

Rulings via Scryfall