Forbidden Rite: This passive grants a boost to Path of exile currency Poison damage when using Chaos spells, making Contagion even more effective for applying Poison while scaling Chaos damage over time.

Malediction: Occultist's Malediction provides access to cursing enemies with Despair (a curse that increases Chaos damage) while also boosting your Poison output.

Chieftain (Fire/Chaos Hybrid with Poison)
Savage Charges (Chieftain Ascendancy): The Savage Charges ascendancy helps with Poison and Fire damage scaling, but you can still use Contagion to trigger Chaos damage. While Chieftain typically focuses on Fire scaling, it can be adapted to cheap Path of exile currency Chaos builds for Poison hybrid setups.