This thread is pretty good.

https://forums.elderscrollsonline.com/en/discussion/370986/buffing-up-the-leeching-bahrahas-curse-build



For a poison theme character--- DragonKnight- poison morph skills + poison based armor sets + Bow poison skills

Monster set: Spawn of Mephala (Fungal Grotto II) - poison dmg and minor fracture AoE

5pc set: Hand of Mephala (Cradle of Shadows) - poison dmg and 50% snare AoE

5pc Defiler Set (purchase on guild vendors) -- spawns a crazy looking poison monster- poison dmg and stun



This website has every set in the game listed. Great for thinking up combination ideas.

https://elderscrollsonline.wiki.fextralife.com/Sets