Arathremia is the last boss before your group is eligible to enter the last boss rooms.
A gold bag from her encounter can have the boots and gloves of the Redeye Set.
Arathremia can be tanked by 1 tank.
Occasionally, she spawns a group of lvl 40 champions adds. Let your maintank AOE taunt them before you cleave.
She also stuns the group from time to time and throws your group up in the air.