2. Make relevant choices — Riftbound Rules

Section 402 — 7 rules

402.1.: If the first part of a Triggered Ability’s effect is “you may,” or “they may,” its controller decides whether or not to perform the Triggered Ability now.
402.1.a.: If they choose not to perform the Triggered Ability now, it is removed from the chain.
402.2.: Make all choices required for this ability, such as targets, modes, or other relevant decisions. See rule 349. Playing Cards for more information
402.3.: If legal options are not available for an Activated Ability, it is not legal to activate it.
402.4.: If there are not enough options to make legal choices for a Triggered Ability that has been put on the chain, remove it from the Chain now. It ceases to be a Pending Item but never becomes a Finalized Chain Item.
402.4.a.: This is not an Ability being countered.
402.4.b.: If there are legal options to choose, the ability’s controller must choose them. They may not decline this stage of playing a Trigger.