Geb

Geb is the stand of N'Dour. It attacks the player and Polnareff (then Jotaro, Iggy, and potentially the player) in the Fertile Crescent.

Event
After finding the downed chopper, you'll enter a battle with Geb's 'Water Claw' using the main character and Polnareff. Beating it here yields a Badge of Honor, but doesn't change the plot. Fleeing is possible, but the enemy's speed is very high so you may have to keep trying. Following a few more scenes, you'll enter a battle against Water Claw again, this time with Jotaro and Iggy. The battle will automatically end either after 15 turns pass, or the party successfully flees.

If you have Sonic Youth, Wildhearts, Miracles, or Mr. Big, you'll get special cutscenes before the second battle. Sonic Youth and Mr. Big will allow you to support Jotaro and Iggy from afar, the former by damaging Geb each turn, and the latter by healing the team. Wildhearts and Miracles will allow you to actually join in the battle along with Jotaro and Iggy. All of these events will give you +2FP with Iggy. In addition, if your Stand is Howlin' Wolf, there will be extra dialogue during the cutscene. There will also be extra dialogue if your Stand is Quicksilver, but only if the Wave Motion Gun skill is learned.