From Guild Wars 2 Wiki
The Shadow Behemoth is a gargantuan creature from the Underworld that breaks into Tyria in the Godslost Swamp, near the sunken Temple of the Ages. It is capable of spawning portals to the Underworld to summon shades and aatxes.
 Skills and abilities
- Annihilation - The Shadow Behemoth will spawn three large circles that pulse every second, dealing damage.
- Summon Portals - The Shadow Behemoth roars and summons three Portals to the Underworld.
- Upon its defeat, a Demonic Chest spawns for any player that contributed to the event.