Boar Beach

This is a hidden area which can only be accessed from the Ancient Valley - Frozen Tundra level. To enter this map, you must locate an open fence in the upper left area of the map. Once there, go to the open section of the fence and press up after waiting for a few seconds. This should enter you into a new area.

This is a reference to the MMO Maplestory, where there is a hidden map called Pig Beach, which has a similar layout.

The entrance only spawns if the bridge in the middle of the map of  Ancient Valley - Frozen Tundra is NOT broken.

Spawns
Toxic Beast Minion

Armored Boar

Mushrum

Sand Crab

Bosses
Toxic Beast