As the triggered ability resolves, first the player whose turn it is chooses a creature or planeswalker they control, then each other player in turn order does the same, knowing the choices made before them. Then all the chosen creatures and/or planeswalkers are sacrificed at the same time.
25-09-2020
wotc
Demon's Disciple can be the creature sacrificed for its own ability.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.