When a card triggers during the process of playing a spell (such as targeting or paying costs), does the trigger resolve before or after the spell that triggered it?

Ruling: When a trigger condition is met during the process of playing a spell (whether from targeting, paying costs, or other activation procedures), the triggered ability is added on top of the chain immediately and resolves before the spell that triggered it.

Sequence:

• The card/ability is put on the chain first (this is the very first step)
• Then you pay costs, choose targets, etc.
• If a trigger condition is met during this process, the triggered ability is added on top of the chain immediately
• The triggered ability resolves first
• Then the original spell/ability resolves

Nuances:

• Targeting is not part of a cost, but it is part of putting a spell on the chain
• There can never be more than one chain; if there's already a chain, effects are always added to it