Aptitude for sin and Animal spells

Ave Sodales,

I require some advice for game balance.

Does the Virtue "Aptitude for a sin" with the particular sin "poisoning people" (which is a canon sample) apply and qualify for a Cr(Re)An spell "Summon the venomous viper" which invoke an asp under the Maga's control (obviously for poisoning purposes).

I would say no. I think an aptitude for poisoning people applies to you trying to poison someone directly, but not you trying to summon a poisonous snake to bite someone.

While darkwing is mostly correct, I'd let you have that bonus is you were specifically summoning that adder for a poisonous plot.
Lab total, not so much though.

To the infernal, intent matters.

I agree with you.

So the Tainted Virtue does not provide +3 bonus for every roll remotely connected to poisoning, but only to specific rolls in limited circumstances. Details need to be decided by the SG, as usual.