XBox 360/PS3/PC: Snailburt is found near the end of the Marsh level, out in the open, just before you see the beefy Peasant.
"Snail's Shell" +5
Defense, -2 Agility; This orb is often considered to be highly invaluable to pure warrior characters. It provides the highest defense boost while lowering your agility critically. Effectively turns the user into a high-defense slow tank. Amplified with the Club.
Snailburt is the first animal orb to be seen in the game, he can be found following the Vet.
Snailburt is the only pet that gives you a natural armor bonus (from +5 Defense) without assistance from a weapon, and natural stat bonuses period.
Snailburt is the only stat pet that subtracts from a stat.
One possible reason that Snailburt decreases agility is that snails in real life are quite slow.