D&Dtools

Area/Effect/Target: Living creature touched
Duration: 10 min./level
Saving Throw: None
Spell Resistance: Yes (harmless)
Tortoise shell grants the armor plating of a tortoise across a creature's torso and a tough, leathery skin elsewhere.
The effect grants a +6 enhancement bonus to the creature's existing natural Armor Class.
This enhancement bonus increases by 1 for every three caster levels above 11th, to a maximum of +9 at 20th level.
The enhancement bonus provided by tortoise shell stacks with the target's natural armor bonus, but not with other enhancement bonuses to natural armor.
A creature without natural armor has an effective natural armor bonus of +0, much as a character wearing only normal clothing has an armor bonus of +0.
Tortoise shell slows a creature's movement as if it were wearing heavy armor.
An elf subject to tortoise shell, for example, would have a speed of 20 feet and would run at 60 feet per round.
The spell affects only a creature's speed; tortoise shell doesn't have an armor check penalty or arcane spell failure chance.