Does Charme cast repeated with temporal Portal Start 2 Showdown 1 by 1 or in Showdown with both charmed units? What if I charm to two different battlefields I control?

When you use Temporal Portal to give Charm the Repeat keyword and move two units, the timing of the resulting Showdowns depends on where the units are moved.

1. Moving both units to the same Battlefield you control

If you move both units to the same Battlefield, they will participate in one single Showdown.

• Reasoning: According to Rule 442.1, a Showdown opens when a Battlefield becomes Contested. When the first Charm effect resolves, the Battlefield becomes Contested and a Showdown is "pending." However, the Chain containing the Repeated Charm must finish resolving all its effects before the game checks for state-based triggers like opening the Showdown.
• Result: Both units arrive at the Battlefield. Once the spell finishes, the game sees multiple enemy units at your Battlefield and opens one Showdown. Both moved units will gain the Attacker designation (Rule 442.1.a.3).

2. Moving units to two different Battlefields you control

If you move the units to two different Battlefields (e.g., one to Battlefield A and one to Battlefield B), you will have two separate Showdowns.

• Reasoning: Each Battlefield is a distinct zone. Since both Battlefields now contain both your units and an opponent's unit, both meet the criteria for being Contested.
• Sequence: Because these are two separate locations, the game will open one Showdown first (usually in the order the active player chooses or by battlefield position), resolve it completely, and then open the second Showdown.

Key Nuances

• Attacker Status: In both scenarios, the opponent whose units were moved becomes the Attacker, and you are the Defender (Rule 442.1.a.1).
• Timing: Charm does not have the Action or Reaction keyword. Therefore, you must play this combo during your Main Phase. You cannot play Charm during an existing Showdown to bring more units in (as confirmed by official FAQ).
• State: The moved units retain their current state. If they were exhausted before being Charmed, they remain exhausted during the Showdown.