Archon Shards: Three Crimson Duration Shards, one Amber Cast Speed Shard, one Tauforged Emerald archon shard for 13 corrosive stacks

With Viral on your weapon and damage-over-time effects like Heat or Electricity, you can imbue Corrosive using the [Lavos] augment. With the [Gauss] augment, you can gain additional Heat, Cold, or Blast damage.