Does moving an enemy to a battlefield I control with mutated Mouser by using Evelyn, Charm, or Blitzcrank all designate my Mouser as defender or attacker?
When you use Evelynn, Entrancing, Charm, or Blitzcrank (assuming "Blitzcrank" refers to Blitzcrank, Impassive) to move an enemy unit to a battlefield you already control that contains your Mutated Mouser, the enemy unit becomes the attacker, and your Mutated Mouser becomes a defender.
According to RiftJudge FAQ #5394, #7275, #8263, and #10761, when you move an enemy unit into a battlefield you control, that enemy unit is the one applying the "Contested" status to that location. Because they are the unit applying the contested status, they are designated as the attacker, and you (the controller of the battlefield) are the defender.
How this affects Mutated Mouser:
- Designation: Because you are the defender in this combat, your Mutated Mouser is designated as a defender.
- Shield 2: Mutated Mouser’s [Shield 2] ability is active because it is a defender, granting it +2 Might for the duration of the combat.
- Tank: Mutated Mouser’s [Tank] ability also remains active, which will force the attacking player to assign combat damage to it first during the Combat Damage step (per Rule 460.2.c.5).
This ruling is consistent regardless of which card (Evelynn, Charm, or Blitzcrank) is used to move the enemy unit, as the outcome is determined by which unit applies the contested status to your battlefield.