Full Umbral [Nidus]. Nothing really fancy here, just a lot of power. I like both Abundant Mutation and Insatiable together, to stack way more damage and make his buildup faster. Arcanes are self-explanatory here. For archon shards, I really like two casting speed yellows and at least one max energy blue. After that, up to you, all the usual suspects work great on [Nidus].

Early Nidus