A trio of Arthur’s knights – Gwalchmei, Drudwas mab Tryffin, and Eliwlod ab Madawc ab Uthur – who were able to complete their quests and achieve their desires through their particularly able use of speech.
Llew is also said to be a member of this group.
Source
Triads of the Island of Britain (Welsh ”Triads”) | 11th century to 14th century
