Can I reveal a hidden Teemo Scout at BF1 when my opponent attacks, then reveal Tideturner at BF2 and use its ability to swap positions with Teemo to save it?

Question

Accepted Answer

Yes — provided you have the appropriate Reaction timing and control of both battlefields, you can play Teemo - Scout from Hidden at BF1 and then play Tideturner from Hidden at BF2; when Tideturner’s play effect resolves it may choose Teemo - Scout at BF1 and swap locations, because Hidden permanents must be played to their hidden battlefield but play effects that necessarily target a different location (like Tideturner’s) may choose freely across battlefields.

You may reveal (play) Teemo - Scout from Hidden at BF1 as a Reaction, and you may also reveal (play) Tideturner from Hidden at BF2 as a Reaction. When Tideturner’s "When you play me... Move me to its location and it to my original location" effect resolves it may target the Teemo - Scout at BF1 and swap them (Tideturner will be played to BF2 per the Hidden restriction, then move to BF1 as the effect resolves).

Opponent declares an attack, creating a window in which Reactions may be played (assumed). Play Teemo - Scout from Hidden at BF1. Because it was Hidden at BF1, it must be played to BF1 [811.1.d.1] and it is playable as a Reaction while facedown [811.6]. Play Tideturner from Hidden at BF2. Because it was Hidden at BF2, Tideturner must be placed onto BF2 as it is played [811.1.d.1] and may also be played as a Reaction while facedown [811.6]. Tideturner’s 'When you play me, you may choose a friendly unit. Move me to its location and it to my original location.' ability is a play effect that chooses a unit. Because its play text can only be satisfied by targeting a unit at another location, rule text allows that target to be chosen freely among available options (so it can choose the Teemo - Scout at BF1) [811.1.d.2]. When Tideturner’s play effect resolves, perform the moves: Tideturner moves to BF1 and Teemo - Scout moves to BF2. Movement choices follow the move-choice rules (choose valid locations) [355.4] [355.4.a].

Whether the swap actually “saves” Teemo - Scout depends on game timing: if damage or a kill effect has already resolved and removed Teemo - Scout before you get the Reaction window or before Tideturner’s swap resolves, the swap won’t save it. Also, if you don’t control BF2 (or control is lost earlier), you may not have been able to Hide/play Tideturner there. Any other replacement or restriction effects (not present in the provided context) could also prevent movement or targeting.

Hidden grants the facedown card Reaction and the ability to be played from facedown as a Reaction [811.6]. When a Hidden permanent is played it must be played to the battlefield where it was Hidden [811.1.d.1], so playing Teemo - Scout from Hidden at BF1 will place it on BF1 and playing Tideturner from Hidden at BF2 will place it on BF2. Tideturner’s play effect explicitly requires choosing a unit at another location and swapping locations; the rules explicitly call out this exact situation as an exception to the usual "choose targets from the same battlefield" restriction and say that the target may be chosen freely among available options because the play ability’s targeting restriction can never be fulfilled at Tideturner’s battlefield [811.1.d.2]. Movement caused by spells/abilities requires choosing valid move destinations (a location other than the unit’s current location where the unit is allowed) [355.4] [355.4.a], and choosing a location when playing a unit is handled at finalization [355.2]. Therefore, provided you have the Reaction timing window and control of the battlefields, you can reveal/play Teemo - Scout from Hidden at BF1 and then reveal/play Tideturner from Hidden at BF2; Tideturner’s play effect may then target Teemo - Scout at BF1 and swap them, moving Teemo - Scout to BF2 and Tideturner to BF1. Keep in mind practical timing: if the attack’s damage or a kill resolves before you get these Reaction plays or before the swap resolves, the swap may not prevent Teemo - Scout from being destroyed.