For twelve years, he kept a bronze bowl hanging from a lone tree by an important river crossing and passing knights would use it as a bell to summon him into combat with them. Turquine would always win, of course. The knight would be imprisoned and his shield hung on the tree as a warning to others.
When Lancelot eventually discovered his brother's jailer, he engaged him in single combat for over two hours. Turquine was so impressed by his unknown assailant's military skill that he offered to end the fight and release all his prisoners for him, with the one condition that he was not the knight whom he hated above all others. This knight, of course, turned out to be Lancelot, because he had killed Turquine's brother. The two therefore fought on until Lancelot finally struck Turquine down. It was considered one of Lancelot's most challenging battles.
In The Once and Future King Turquine's count on prisoners was 64 knights, including Sir Lionel.