Level 4 Key Sphere

Steal - Nemesis (Monster Arena)
Rare Steal - N/A
Drop - Seymour Flux (Mt. Gagazet)
- Spectral Keeper (Yevon Dome)
- Omega Weapon (Omega Ruins)
Rare Drop - Land Worm Inside Sin)
Bribe - Chimera Brain (Calm Lands)

To break the HP limit you need to mod armor with 30 Wings to Discovery

Wings to Discovery

Steal - N/A
Rare Steal - N/A
Drop - Shinryu (Monster Arena)
Rare Drop - N/A
Bribe - Marlboro (Calm Lands, Cavern of the Stolen Fayth)
- Great Marlboro (Inside Sin, Omega Ruins)

* 30 for geting 3 chests at chocobo racing