If my opponent has a Dazzling Aurora, and with the end step trigger on the chain, I respond with a Bone Skewer from hand, what happens if the Bone Skewer resolving initiates a showdown?

When you respond to your opponent's Dazzling Aurora trigger with Bone Skewer (played from Hidden), the following sequence occurs:

1. Dazzling Aurora triggers at the end of the turn and is placed on the chain.
2. You play Bone Skewer from Hidden. According to Rule 811.6, a card played from Hidden gains [REACTION] and may be played at any time a card with [REACTION] can be played (which includes during a Closed State).
3. Because you are playing Bone Skewer as a [REACTION], it is placed on top of the chain, above the Dazzling Aurora effect.
4. The chain resolves in LIFO (Last-In, First-Out) order:
   • Bone Skewer resolves first: You choose a battlefield and force your opponent to play a unit from their hand to it.
   • If this action causes a battlefield to become contested, a Showdown is staged. However, per Rule 344 and Rule 344.2, the Showdown cannot initiate while items remain on the chain.
   • Dazzling Aurora resolves next: Your opponent plays a unit to a battlefield.
5. Chain is now empty: Once all chain items have resolved and the game state returns to neutral, the staged Showdown can officially initiate.

Important Considerations

• Showdown Initiation: As per RiftJudge FAQ #9150, #5710, and #1207, Showdowns only initiate when the game reaches a "Neutral Open State" with an empty chain. Even if playing the unit via Bone Skewer creates a contested state, the Showdown is held in a "pending" status until the Dazzling Aurora effect completes and the chain is empty.
• Contested Battlefield: Since you played the unit to a battlefield that now contains units from both players, it is contested. This will open as a Combat Showdown (Rule 456.3).
• Legality of Play: Your opponent may play their unit from the Dazzling Aurora trigger to the same battlefield where you placed the unit via Bone Skewer. As noted in RiftJudge FAQ #1207, combat will not begin until all effects from that unit's "When you play me" trigger (if any) are also resolved.

Note: I could not fully verify this ruling against the retrieved rules. Specifically, the stun effect of Bone Skewer and the reveal mechanic of Dazzling Aurora are not explicitly supported by the provided context.