Unlocking Poison as a Rogue

[Sines]

I've yet to get a definitive answer on this one. Do you get access to the Poison tree if you first side with the Assassin Lord as a class that can use it? Or would I need to start another character? I want poisons if I'm going to play a Rogue class (or even an Archer), but if it needs to be unlocked on a different character, I'll happily start a different character next.

[HousePet]

It should unlock instantly on your character if applicable.