Tiamat's Lair

Tiamat's Lair, also known as the Cave of Greed, is the divine realm of Tiamat. It is located on the first layer of The Nine Hells. The realm consists of an enormous convoluted cavern that contains the lair of the Dragon Queen and, at some distance, those of her various petitioners and other inhabitants.

Geography

The realm consists of a large cave system within a tall mountain, hidden in the hills of Avernus. It holds the only known portal that leads to the second layer, Dis. The caves are littered with Tiamat's own treasure hoard, which lies scattered on the floor throughout the complex.
Tiamat's Lair is patrolled from the sky by numerous flights of dragons. The portal to Dis is guarded by Tiamat herself. She only allows those who offer her a worthy sacrifice to utilize the portal.