Ornn, Blacksmith

Ornn, Blacksmith reads "When you play me or when I hold, look at the top 4 cards of your Main Deck. You may reveal a gear from among them and draw it. Then recycle the rest." The "you may" here doesn't appear in the appropriate place to be part of the sequence, so it is not a decision made when the ability triggers and instead is made when ability resolves. This ability can be split into "When you play me or when I hold," and "look at the top 4 cards of your Main Deck. You may reveal a gear from among them and draw it. Then recycle the rest."

383.3.a.3. If "you may" or "they may" appears in any later part of the Effect of a triggered ability, it is decided on resolution. Example: Ornn, Blacksmith reads "When you play me or when I hold, look at the top 4 cards of your Main Deck. You may reveal a gear from among them and draw it. Then recycle the rest." This "you may" does not appear as the first part of its effect, so the choice is made on resolution. The ability is always finalized to the chain.