Neslug (Final Fantasy X)

Neslug is an optional enemy in Final Fantasy X, bred in the Original section of the Monster Arena after at least one of each fiend roaming throughout Spira is captured. The design for Neslug, a hideously mutated snail, is only found here; hence making him the only true 'Original' monster.

After losing half his HP, Neslug will retreat into his shell and initiate Auto-Regen and regenerate massive amounts of HP. During this time he is also immune to Physical Attacks, leaving Ultima and Anima's Pain very handy. When he is down to 1,000,000 HP his shell will break and disappear. Wakka's Attack Reels Overdrive is a useful way to ensure victory.