FFXII - Espers - Cuchulainn, the Impure

Vrishchika Ascendant
Scion created to rid the world of its impurities by swallowing them within himself, in opposition to Nabriales the Majestic, scion of light. The world, however, was more filled with impurity and corruption than even the gods dared imagine, and having swallowed it all, the once beautiful Cúchulainn was transformed into a hideous thing, a deity of filth, and so did he turn against his creators. Wherever his feet should fall, there all life withers to dust.

Previously seen in: Final Fantasy Tactics as one of the Lucavi (Queklain).

Location: Where to find: Garamsythe Waterway, No. 1 Cloaca. After completing the White Mousse mark hunt and receiving your prize (Sluice Gate Key), return to Central Waterway Control. Three things to do:

(1) Close the No. 3 and No. 10 sluice gates. Go down to No. 3 Cloaca Spur and touch the No. 1 South Waterway Control (it's a stone pedestal.)
(2) Return to Central Waterway Control. Open up the No. 3 and No. 10 gates, and close the other two (No. 4 and No. 11). Go down to No. 4 Cloaca Spur and touch the No. 1 North Waterway Control.
(3) Back to the Central Waterway Control. SAVE YOUR GAME. With the North & South Waterway Controls open, the way to the esper is opened when the No. 3 and No. 4 controls are on (in other words, their sluice gates are closed). So make sure it's just those two on, with No. 10 and No. 11 off. Go down the No. 1 Cloaca and.. there he is.

Battle info
Status: Protect, Shell, Haste, Regen
Steal: Scorpio Gem
Attacks: Disablega, Immobilizega, Regular (~650), Bio (~600 range + Sap), Mana Spring (?), Invert, Malaise (~600 drain), Slowga
Stipulation: Constant HP loss (That is, a permanent Sap-all without the Sap status)
LP received: 50
LP required to learn: 50

Advice: Start with Dispel, and get to work. "Foobars" (Level 44, HP 6545, Weak: Holy) spawn around him occasionally and cease after a point, but take them out anyways. While his attacks don't do much damage, the fact you constantly lose HP should be your primary concern. I imagine the HP loss gets amplified if "Sap" is inflicted, I didn't make a note of that. Disablega and Immobilizega are true headaches, so have Esunaga ready, preferably for all your characters: if anyone isn't Disabled, it'll be up to them to save the rest. If all three get disabled, you'll have to swap in someone else to do the job. Regen might help slow down the unstoppable HP loss, but in any case, so long as you make sure your HP never drops below 1,000 you should be fine.