Fungi Beast
The Fungi Beast is an Act 1 enemy with 27-31 HP. It primarily uses Bite (5-7 damage) for offense. Its defining mechanic is Spore Cloud: when the Fungi Beast dies, it applies 2 Vulnerable to the player. This death effect is unavoidable and triggers regardless of how it was killed.
The Fungi Beast's death-triggered Vulnerable is the key consideration when fighting it. In multi-enemy encounters, killing the Fungi Beast first may leave you Vulnerable when facing remaining enemies, while killing it last means it is attacking you with Bite while you deal with other threats. Mitigating Vulnerable with Block-heavy turns after it dies, or having the Turnip relic (prevents Frail) is useful context — though Turnip does not help with Vulnerable. Planning to have strong Block on the turn the Fungi Beast dies is the best approach.