Unfortunately you can not add AI because they have bleed. A Triton can get a Poison ability, AI, and Chiv.
You can now put Chiv or another magic like Mysticism on it but the Poison Melee will go away but the poison skill will raise and be used with Venomous Bite.
They kill stuff but not as well as Chiv and AI.
Here is what you can do with poison on a Cu:
How to access poisoning abilities on your Cu Sidhe.
If you choose Poison as a Magic choice before you put any abilities on the pet, You open some new choices.
Aura of Nausea
Trains the creature in the Aura of Nausea area effect, causing nearby targets to suffer a reduction in swing speed, hit chance, defense chance and faster casting.
Poison Breath
Trains the creature in the Poison Breath area effect, causing lethal poison to nearby targets.
Essence of Disease
Trains the creature in the Essence of Disease area effect, causing poison damage to nearby targets.
Venomous Bite
Trains the creature in the Venomous Bite special ability, causing the creature to poison all nearby targets.
Vicious Bite
Trains the creature in the Vicious Bite special ability, causing the creature to inflict a festering wound on approaching targets that does direct damage over time.
You can only choose one of these abilities!!!
After you choose One. You can not choose any more abilities. You can not choose an ability and then choose poison and get these choices. You can not get Armor Ignore and one of these on your Cu.
You can choose one and your Cu will have a new ability.
After you choose one of these. You can now choose a different Magic. You lose poisoning but not the ability.
5 more things you can try on your Cu.