Ajani's Last Stand is a rare Enchantment card from Core Set 2019 (M19), collector number 4. Current market price: $0.28 (foil $0.15), TCGplayer market prices via Scryfall.
Whenever a creature or planeswalker you control dies, you may sacrifice this enchantment. If you do, create a 4/4 white Avatar creature token with flying. When a spell or ability an opponent controls causes you to discard this card, if you control a Plains, create a 4/4 white Avatar creature token with flying.