Vashna
First lord of the Darklords in Lone Wolf. Slain by Ulnar I in times long ago. Is subject to repeated attempts to revive/recall his spirit, in Lone Wolf gamebooks 4 and 16 and Legends of Lone Wolf 8 (if I remember the numbers right). Presumably extremely powerful.
Also makes a good swear-word.
"In Vashna's name..."
"By Vashna, I'll kick your ass!"
"In Vashna's name..."
"By Vashna, I'll kick your ass!"