Menw fab Teirgwaedd, - fab Teirwaedd
Menw throws a spear at Ysbaddaden which is poisoned, and he shape-shifts into a bird during the epic hunt of Twrch Trwyth.
Each member of the party was chosen for his particular skills, and Menw fab Teirgwaedd was chosen for his mastery of magic, which would preserve the party in foreign and heathen lands because he could render them invisible.
Menw shows up several times in the Triads as a shapeshifter and an enchanter. The Triad no. 28 says he learnt the skill of shapeshifting from no other than Uthyr Pendragon.