How does playing Tideturner work if the opponent has Vex, Apathetic at a Battlefield?

When you play Tideturner at a battlefield where an opponent controls Vex, Apathetic, the interaction depends on the turn order, which determines the placement of triggered abilities on the chain.

The Interaction

Both the "When you play" ability of Tideturner and the "When an opponent plays a unit" ability of Vex, Apathetic are triggered abilities that occur simultaneously. Per Rule 303.2.a, turn order dictates resolution:

1. The Turn Player places their triggers on the chain first.
2. The Non-Turn Player places their triggers on the chain on top.
3. The chain resolves Last-In, First-Out (LIFO).

Sequence Scenarios

If the Turn Player plays Tideturner:

1. Chain Placement: The Turn Player's Tideturner trigger is placed on the chain first, followed by the Non-Turn Player's Vex trigger on top.
2. Resolution: Vex’s trigger resolves first, stunning Tideturner and applying the restriction that it cannot move this turn.
3. Outcome: Because Tideturner is stunned and restricted from moving, its ability to move and swap locations fails.

If the Non-Turn Player plays Tideturner:

1. Chain Placement: The Turn Player's Vex trigger is placed on the chain first, followed by the Non-Turn Player's Tideturner trigger on top.
2. Resolution: Tideturner’s trigger resolves first, and the swap completes successfully.
3. Outcome: Tideturner completes its move and swap, then Vex’s trigger resolves to stun Tideturner at its new location.

Important Considerations

• Stun Effect: According to Rule 423.1, a stunned unit cannot contribute might to combat. Furthermore, Vex, Apathetic includes a specific restriction stating the unit cannot move for the remainder of the turn.
• Partial Resolution: If Tideturner is stunned before its move trigger resolves (as in the Turn Player scenario), the swap fails to execute because the movement is prohibited. If the swap were to involve a second unit that was not restricted, partial resolution rules might apply to that unit, but Tideturner itself would remain where it was played.

This interpretation is based on RiftJudge FAQ #10318 and Rule 303.2.a.

Note: I could not fully verify the specific ability text of Vex, Apathetic against the retrieved rules.