An Undying Pledge

After the cutscene with Stray Cloud, try to exit Norg into the SSG, you will be stopped by another cutscene.

Following this cutscene, head to K-6 on the first map of the SSG (go east a bunch first, past the hidden door towards the jungle, then turn right around K-5ish). Here you'll find ??? which spawns a kraken type monster when you touch it.

Be warned, not all 75 jobs can solo him easily. I recommend doing this with at least a pair, to avoid any trouble. (Blm, Smn, Rdm, Bst, Nin, and War/Nin should be fine, maybe some others). I estimate he has 5000 HP. As a 75 Rng I got hit with a 650-damage attack of some kind, which was rather nasty, thanks to Division (was it?) and his pals, who helped me out.