1. Crafting Stations Related to Chaos and Poison
Ervig's influence as a fungal and chaos-based boss can lead you to POE2 Currency crafting stations or systems where you can focus on chaos damage, poison resistance, or fungal-themed items. These may include:

Chaos Workbench: A crafting station that allows you to imbue your items with chaos damage or enhance the chaos resistance of your gear. You might also be able to craft poison-related affixes like increased poison damage over time or poison duration.
The Fungal Anvil: While not necessarily in the game, this could be a potential crafting station for poison-themed gear. This station might let you upgrade items with increased poison effect, chaos damage, or damage over time boosts for poison-based builds.
2. Vendors Specializing in Chaos or Poison Gear
There might be specific vendors or crafting NPCs who specialize in selling items that enhance poison or chaos builds, as a thematic tie-in to defeating Ervig. These vendors could offer:

Poison and Chaos Rings/Amulets: Vendors in town or in special zones could sell jewelry that enhances chaos damage or poison resistance.
Chaos Scrolls: Similar to vendors who sell currency items, there may be specific chaos-related scrolls or consumables that allow you to alter your gear to have poison-related properties.
Fungal-themed Items: You may encounter an NPC offering special gear or consumables related to fungal themes, such as fungal armor sets, chaos damage modifiers, or poison resistance potions.
3. Crafting Materials Dropped by Ervig
Defeating Ervig might grant access to chaos or poison-related crafting materials that can be used to enhance or craft items specifically useful for builds focused on poison or chaos damage:

Rotting Spores: A material dropped by Ervig that could be used to upgrade or craft gear with poison damage enhancements or additional chaos resistance.
Fungal Essence: A rare material that can be used to augment chaos damage or poison duration on weapons, armor, or accessories.
4. Special Crafting Services
After defeating Ervig, certain NPCs or special vendors may offer services to re-roll or augment specific chaos or poison-themed items. They could offer:

Re-roll Chaos Stats: An NPC who lets you re-roll chaos or poison-related mods on weapons and armor to enhance your build.
Craft Poison-Infused Items: Vendors or crafting stations that allow you to add poison-related effects or chaos damage over time to your gear.
5. Additional Vendors in the Grim Tangle
If you continue to explore the Grim Tangle, you might find vendors who focus on selling materials or upgrades related to the fungal and chaos theme of Ervig's influence, giving you easier access to POE2 Currency for sale high-level items needed for crafting or enhancing poison builds.