High Troller

One a spell or ability has had random targets chosen, a player can’t choose to not finish casting or activating that spell or ability unless there’s no way for the player to complete the process. For example, the player can’t choose to not activate mana abilities to pay for the spell.

If a spell or ability has “any number” of targets or “up to” a given number of targets, first its controller choses how many targets it has. If that number is greater than zero, the targets are chosen randomly.

A triggered ability won’t cost less, since there isn’t a triggering cost to reduce, but its targets will be chosen randomly.