1. Weapons
Ervig's loot pool for weapons can include:

Poison/Chaos Damage Weapons: Typically, you can find wands, staves, or POE2 Currency daggers that increase poison or chaos damage. These can be powerful for builds focusing on these damage types.
Elemental Weapons: Some of his loot could include items that add elemental damage, particularly chaos or fire damage, which synergizes with his toxic abilities.
Cursed Weapons: Items with special curse-related bonuses or the ability to inflict poison or chaos-based curses on enemies could also be a potential drop from Ervig.
2. Armor
Armor drops can vary, but are usually focused around the following themes:

Resistant Armor: Gear with added chaos resistance or poison resistance would be common, given Ervig’s poison-based attacks.
Life Regeneration: Armor that boosts life regeneration or energy shield regeneration could be useful for builds focusing on sustainability in longer fights.
Elemental and Chaos Armor: Look for armor that boosts chaos resistance, poison damage, or chaos damage over time for builds centered around chaos-based combat.
Fungal Themed Gear: Armor might feature aesthetics or special effects that reference the fungal nature of the fight, perhaps adding poisoned effect duration or fungal growth-based skills.
3. Accessories
Ervig's loot pool for accessories could include:

Rings, Amulets, and Belts: These items may boost chaos damage, life regeneration, or poison resistance. Some accessories might also boost your maximum energy shield or maximum life.
Unique Poisons/Chaos Rings: There could also be rings that offer specific poison-related bonuses such as increased damage or reduced poison duration on you.
4. Special Loot - Ervig's Signature Gear
Ervig may drop unique, signature items themed around his druidic powers:

Ervig’s Staff: A staff that could have significant poison-based abilities or amplify chaos damage.
Rotting Essence: An item or consumable related to fungal, chaos, or poison-based crafting.
Fungal Afflictions: Unique gear or enchantments that grant poison damage, chaos-related buffs, or increase chaos resistance.
5. Potential for Crafting Materials
Ervig’s drops might also include crafting materials tied to his poisonous nature:

Fungal Spores: Could be used in crafting recipes to upgrade gear with chaos, poison, or buy POE 2 Currency fungal themes.