The Lich's lair is the home of the Lich, before he was trapped in amber. Princess Bubblegum states in "Mortal Folly" that the Lich lives in the remains of his tower, implying that there was once a tower attached. From inside and out it is clearly an old subway station from before the Mushroom War, complete with broken-down subway cars. The Lich's Lair is protected by skeleton guards who appear to be the remains of those lost to the Mushroom War.
In "Mortal Recoil" this is a scene crime and this is a location where the rag doll princess take back all pieces of Finn's Pack and restored and sew that.
In the episode "His Hero," there is a flashback of the hero Billy casting down the Lich in what appears to be a castle-like hallway. It is unknown where this scene takes place, but it may be in the tower part of the Lair that was once there. This rundown area is found beyond Iceberg Lake.
Well of Power
The Lich's Well of Power is located on a lower floor. The Lich uses the well to regain his evil powers after being imprisoned in amber. It appears to be set in an area that once held a turnabout for subway trains due to the subway tracks nearby. The well is fed by a dripping pipe above it, and (according to Jake) it is filled with "toxic waste." It is similar to the concoction of gasoline, bleach, plutonium and other hazardous chemicals that the Lich later uses in "Mortal Recoil." They supposedly could be left over from the Mushroom War. It is possible that the Well of Power is the spot where the mushroom bomb from the Mushroom War hit.
- According to Princess Bubblegum, the lair is very cold.