Toxic

A creature with this trait has corrosive blood or other exotic defensive mechanisms that inflict harm when it is struck.
A character that successfully deals damage to a Toxic creature in melee combat must make a Toughness test at the end of his turn with a penalty equal to 10 times the number in parentheses (X), or suffer 1d10 points of Energy damage not reduced by Armour or Toughness. For example, a creature with Toxic (4) would impose a –40 on Toughness tests.
Some creatures carry additional effects with their toxins, or inflict more damage as indicated in their individual descriptions.