Gelzebas was recruited by Rogles at some unknown point of the time before the events of the first game.
In the trailer, Gelzebas attacks Yuuko along with many other monsters but they are easily defeated. In the game, Rogles gives him a Phantasm jewel and the mission of guarding the Volcanic tunnel area. In order to get the last Phantasm jewel, Yuuko had to face him after entering to this area. The Valis warrior ended Gelzebas's life during the fight and claimed his Phantasm jewel.
Not much details are given about Gelzebas's personality. He is shown to be very aggressive in the trailer. Although in the game he is seen in a challenging position idling, meaning that he is a powerful and important general and possibly the most powerful one of all of Rogles's generals in this version, as he is the last general fought before entering to Rogles's castle.
Gelzebas can spread many energy balls by extending his wings. He can also summon enemies to assist him in battle.
Gelzebas only appeared in the Famicom/NES version of Valis I (in both the trailer and the game itself) as the fifth boss guarding the Volcanic tunnel area. Defeating him grants the player the access to the Valis sword's last upgrade and the last Phantasm jewel from the game to access Rogles's castle.
- Gelzebas is the tallest of all the bosses in the version of the game he appears in.
- Gelzebas is the only one of Rogles's generals in the trailer to not be cut in half by Yuuko, He possibly retreated before she could do so.
- Gelzebas is the only antagonist from the series to have the ability to summon enemies as helpers.
- Gelzebas is the only one of the bosses to remain in the same position where he appears during his entire battle.
- If the player positions Yuuko right below Gelzebas and makes her crouch while attacking him, Gelzebas can be defeated in a matter of seconds.