A Present Mimic is a type of Mimic that spawns during the Frost Moon. It acts like other Mimics, trying to pass itself off as a present.
Present Mimics are rarer than the other monsters spawned during the Frost Moon. The reason seems to be how all Mimics initially behave like still objects. This causes the Present Mimics to spawn off-screen and, unlike the other monsters, stay there until the player gets near it or somehow damages it. A Water Candle and Battle Potions may help increase the number of Present Mimics.
Present Mimics drop large amounts of hearts. This can be very convenient during the fight.
Present Mimics do not run away once night is over like most other Frost Moon monsters do. It will chase the player until killed (given the player does not lose sight of it).