Morbid

Morbid is an ability word introduced in Innistrad. It signals that a spell or ability has different effects, additional effects, or may only be used if a creature has died earlier in the same turn.

History
After Innistrad, morbid was also featured in Dark Ascension, Conspiracy, Commander 2014 and Modern Horizons. It was featured as the BG draft archetype in Core Set 2021, although without the ability word.

Rulings

 * Morbid abilities merely check if a creature died earlier in the turn. The creature card doesn't need to still be in the graveyard.
 * Token creatures can also die, going to their owner's graveyard before ceasing to exist.
 * Some morbid abilities that appear on instants and sorceries use the word "instead." The spells have an upgraded effect when they resolve if a creature has died earlier in the turn. You only get the upgraded effect, not both effects.
 * Some morbid abilities are activated abilities of permanents. To activate such an ability, a creature must have died earlier in the turn.
 * Triggered morbid abilities use an intervening "if" clause. A creature must have died earlier in the turn in order for these abilities to trigger; otherwise, they do nothing. In other words, there's no way to have the ability trigger if no creature has died that turn, even if you intend to have a creature die in response to the triggered ability.
 * Using Morbid allows a card to be state-based as long as conditions are met.