Source: Dungeon Master's Guide

Armor (Any Light, Medium, or Heavy), Rarity Varies (Requires Attunement)

Bound into this armor is a spell of level 8 or lower. The spell is determined when the armor is created and must belong to the Abjuration or Illusion school of magic. The armor has 6 charges and regains 1d6 expended charges daily at dawn. While wearing the armor, you can expend 1 charge to cast its spell.

The level of the spell bound into the armor determines the spell’s saving throw DC and attack bonus, as well as the armor’s rarity, as shown in the following table.

Spell Level Rarity Save DC Attack Bonus
Cantrip Uncommon 13 +5
1 Uncommon 13 +5
2 Rare 13 +5
3 Rare 15 +7
4 Very Rare 15 +7
5 Very Rare 17 +9
6 Legendary 17 +9
7 Legendary 18 +10
8 Legendary 18 +10