Glabbagool

Glabbagool was an unusual sentient gelatinous cube in the Oozing Temple sometime in the late 1480s or early 1490s DR.

Personality
The arrival of the demon lord Juiblex in the Underdark somehow granted Glabbagool sentience. It wanted to avoid fighting, however, and was genuinely curious about the world and the people that inhabited it.

History
Glabbagool was a gelatinous cube in the Oozing Temple. When Juiblex arrived in the Underdark, it was granted sentience. It may have met and befriended a party of adventurers escaping the drow slavers of Velkynvelve, even offering to travel with them or gift them a magical mace located within its oozing form.