Source: Critical Role - Call of the Netherdeep

Armor (any medium or heavy except hide), very rare (requires attunement)

This magic armor has a dull, rusty color or has veins of ruidium running through it. While you wear this armor, you gain the following benefits:

• You have resistance to psychic damage.
• You can breathe water.
• You gain a swimming speed equal to your walking speed.

Ruidium Corruption. When you roll a 1 on a saving throw while wearing this armor, you must make a DC 15 Charisma saving throw. On a failed save, you gain 1 level of exhaustion. If you are not already suffering from ruidium corruption, you become corrupted when you fail this save.

If Ruidium Is Destroyed. If the Apotheon is killed or redeemed, all of the ruidium in Exandria is destroyed instantly, and Ruidium Armor becomes +1 Armor .