Once per game, in any Assault phase, a unit with this biomorph can unlease its toxic miasma. If it does so, at the Initiative 1 step, all enemy units engaged in close comabt suffer a number of hits equal to the number of models from their unit in base contact with any model from the Tyranid unit unleashing the toxic miasma. These hits are resolved at Strength 3 AP- and have the Poisoned and Ignores Cover special rules.
Regeneration:
At the end of each friendly turn, roll a D6 for each model with the regeneration biomorph that has less then its starting number of Wounds, but has not been removed as a casualty. On a 4+, that model regains a single Wound lost earlier in the battle.