Anti Buff Mode is a new gamemode introduced in AlchemistNPC which gives you immunity to almost all buffs from potions. That fact adds a certain plane of complexity to the game, disallowing you to use potions to enhance yourself.
It is activated by using the Anti-Buff item, which will appear in a newly spawned player's inventory. When mode is active, boosters can be used for permanent boosts.
- Anti-Buff Item