Ambrosia

Ambrosia is an orange magical liquid rarely found in flasks underground. A creature stained with it blocks absolutely all health damage. It wears off very quickly with movement, so is best used while standing still. Drinking it will not give you invincibility, instead it will simply cause food poisoning.

It should be mentioned it provides no protection against offensive effects that do not do health damage, and other liquids can wash it off, making you vulnerable again.

Tips

 * Provides immunity against the damage from cursed rock, making travel to the parallel worlds significantly easier.
 * Due to how quickly it wears off, it is best used when anticipating damage, such as before using a particularly dangerous spell like Nuke.
 * Note that since acid or lava do not "stain" you, it is possible to use Ambrosia to immerse yourself in these materials and fill a flask with them, as it should not wash off. Take care to watch your stain amount.
 * Using Teleport Spell does not count as moving, so won't reduce the stain level. This means that you can be protected more or less indefinitely as long as you're only teleporting around. Note that the slight movement from falling after teleporting to midair (or slightly off the ground) will still count, so it is difficult to teleport with no 'movement' at all.
 * The effects of this potion even protect you from the normally insta-kill explosion that happens from exceeding 200% satiation, allowing the player to explode multiple times in a row.

Trivia
While it cannot be consumed to gain protection these days, this was actually possible when it was first introduced. As effects from consumption cannot be washed off and are not dependent on movement this basically meant you had godmode active for the duration, enabling you to swim long distances in lava and rush headlong into danger without much worry.