Zarkon= The ruthless, cold, Emperor of the Galra Empire, ruler of most of the known universe. Xarkon spent the last ten thousand years conquering it. He desires the Lions of Voltron (Prior Black Paladin). 
The Yellow Paladin, pilot of the Yellow Lion is Hunk: engineer, gentle giant with an equally large appetite. Coran: Royal advisor to Princess Allura, Coran is last male Altean, eccentric, silly, excitable.
Quintessence is a substance with the highest known energy per unit volume. Powers all.