Carnal Snake is a sub-boss found on the 228th floor of Tartarus in a group of three. They impede the party's progress and must be beaten to proceed. After the Shadows are beaten, the Judgement Social Link will increase to level 5. The Carnal Snake later reappears as a normal enemy in the Adamah Block of Tartarus, between floors 237 to 261.
For an easier time against the boss, pick Aigis, Junpei and Koromaru to be in the party. Assign Aigis to a support role and make Junpei and Koromaru only use physical attacks against the enemy. The boss will be occupied nullifying Junpei's and Koromaru's fire resistances and all the buffs Aigis gives the party, giving the party enough time to attack them.
Persona 4
Carnal Snake appears in Paradise 3 and 4 in Heaven within the Midnight Channel. Like other snake Shadows, they will try to follow Stagnant Air up with status ailment abilities, with these causing Poison. They also possess the Life Leech skill, a stronger version of Life Drain and may prioritize Life Leech over Stagnant Air if damaged. Defeating a Carnal Snake may yield a Scorching Scale. Selling 10 Scorching Scales will unlock the Adoracion ougi for Yukiko Amagi.
In Golden, it appears in Paradise 1 to 4. It may drop Meteorite for trade at Shiroku Pub.