Baron Tass is an overweight Thunderian man. He arrived on New Thundera and tried to cash in on old debts. Lion-O forbid him though. He is shown to have a history with Torr. He and Mr. Grubber found the location of his old estate and used water from the Well of Doubt to make the Lord of the ThunderCats doubt himself. Once this was discovered by Jagara, she helped Lion-O overcome his doubts when Baron Tass and Mr. Grubber attacked with some stone statues. After the stone statues were destroyed, Baron Tass promised to change his ways.
- Well of Doubt (first appearance)