The name Galenos appears to have no obvious connotations: the only famous historical Galenus was a doctor of medicine. Tuatha dé, on the other hand, is an Irish term which translates as "people of the god (insert name)", as in "Tuatha dé Danann"- the people of the goddess Danu.
Galenos has so far only appeared during council meetings within the Chamber of the Celestial Sphere and during the assault on the Relic at Mount Minakami where he was seen spewing fire.
No information currently available.
Little is known about Galenos' powers. As a Zoalord, he is able to control Zoanoids telepathically and he was shown breathing fire during the attack on the Relic. His battle form has yet to be displayed.