Ring of Greater Invincibility

The Fire MageFire MageNPC · Level 6 · 100 HP · Castle Ruins DragoDragoMerchant · Level 50 · 376 HP · Old Camp wears one in the Old Camp castle, and so does GomezGomezNPC · Level 100 · 400 HP · Old Camp, who leads the Old Camp guards. Baal CadarBaal CadarMerchant · Level 30 · 376 HP · Swamp Camp sells it in the Swamp Camp in chapter 4, and StoneStoneNPC · Level 13 · 220 HP · Old Camp may give you one after you free him from the castle dungeon.