Showcasing a pet project of mine this league - getting high on aoe scaling and covering the entire screen with contagion!

Pob: https://pobb.in/dJTRCWwFIlcS

Scaling the AoE of Contagion via quality and area of effect.
Quality = 23% from gem, 40% from lv6 enhance (lv4 + socketed in Viridi's veil), 27% from ashes.
Bog Shaman gives us 50% aoe. We use Unnatural Instinct to grab 36% aoe from scion start and Elementalist Convergence FF/FF to grab 60% aoe. Our medium clusters also give tons of aoe.

The rest of the tree is normal damage scaling for chaos dot. The single target isn't good but can be improved when I get a better staff.

Defensively I've decided to go evasion with an okay-ish necrotic armor base, getting into Grace with 50k evasion total.

The build plays a lot better with Mageblood flasks, but it's doable without. You will lose some QoL and evasion. Inplace you can use a crystal belt with good suffixes. The build can be stronger (both AoE and damage) in Settlers with Occultist.