Brandt's Doppelganger mostly uses physical attacks against the player. The player should watch out for the enemy when it casts Berserk on itself, since this can cause the Doppelganger's physical attacks to deal more damage. Similar to the other Doppelganger enemies, the Doppelganger's physical attacks may inflict the Suppress and Curseailments. When the enemy's HP begins to fall, the Doppelganger will cast Cura on itself. When it is encountered in the Witch's Mansion as a boss, the Doppelganger receives higher stats and can attack twice per turn.
When fighting the enemy, it is highly advised of the player to equip a Darksteel Shield to all party members. To defeat the Doppelganger quickly, the player should attack light-elemental weapons and spells.