Terraria players can consume an Obsidian Skin Potion to gain fire resistance. Doing so grants them the Obsidian Skin buff. When active, the buff provides immunity to the following statuses: Hellstone Lava On Fire! Debuff Meteorite You may cancel the potion’s effects early, and the duration als...
with the punch, so to speak. It's not that Tarnac is more immune to the Long Sword... it's that he's more of a seasoned warrior and that he's learned how to resist the pain, shift his body so that the blow is less lethal. And, sure, his skin is probably a bit tougher too...