The Megapithecus Arena is an arena for fighting the second boss, the Megapithecus. The Megapithecus is not the only danger, however. Freezing temperatures (around -4 °F/-20 °C) also pose a hazard to survivors, so come prepared with good hypothermal protection.
The Megapithecus Arena itself is located beneath the blue Obelisk, but you can open the portal to the arena from any Obelisk or Beacon unless you're playing in Single Player mode, in which case you will need to travel to the blue obelisk.
Tribute Requirements
The following items are needed to summon the Megapithecus:
These restrictions do not apply to Extinction arena as the boss fight takes place inside the map rather than in a separate section of the map
Entry Restriction:
A maximum of 10 survivors and 20 creatures are allowed to enter the arena. In the case of Tek Cave, a maximum of 10 survivors and 40 creatures are allowed, but only 20 creatures can be warped in at any point of time to the arena itself per warp.
Most Arenas restrict survivors to ground-only creature. There are a few exceptions:
Genesis - Sea Creatures are permitted in Moeder arena, and its drag weights are not considered when warping to the arena.
Exceptions for certain arenas are only valid for the listed arenas. E.g. Manticore Arena refers to the Manticore Arena in Scorched Earth but not Ragnarok Arena where you also have to fight against the Manticore.
A creature's "drag weight" must be less than 560. This is how much the creature itself weighs, not its carrying weight seen in its inventory.
To see this value in-game, place the creature on an Elevator Platform with an empty inventory and no saddle.