Bio-poison is a non-standard damage type used exclusively by Templars. No current enemy uses Bio-poison in its attacks, and it is not currently an environmental hazard on any missions. For this reason, Templars do not need Bio-poison Res.
Like all non-standard damage types, rolls for dealing Bio-poison damage range between 30% and 100% of the stated damage. This differs from bonus damage from other sources which is from 0% to 100% of the stated damage. This, combined with the fact that non-standard damage types ignore armor makes it a powerful method of dealing with most foes. (Non-standard attacks do have to contend with opposing Resistance and Res, but those are usually very weak defenses.)
If the attack damages the target, the toxins are delivered. For three turns, at the end of their turn the target will suffer Bio-Poison damage equal to the attack's Bio-Poison rating, reduced as normal by their Resistance and Bio-Poison Res. If an enemy target is reduced to 0 HP by the residual damage of Bio-Poison, they die at the end of their turn.