Starmetal Greataxe

Weapon (greataxe) , Legendary (unique) requires attunement by a paladin

Crafted by the greatest of the Mystic craftsmen for their war against the Void, the Starmetal Greataxe is a semi-sentient weapon, using its mental abilities to assist its wielder.

Defender.  You gain a +3 bonus to attack and damage rolls made with this magic weapon.

The first time you attack with the axe on each of your turns, you can transfer some or all of the axe’s bonus to your Armor Class, instead of using the bonus on any attacks that turn. For example, you could reduce the bonus to your attack and damage rolls to +1 and gain a +2 bonus to AC. The adjusted bonuses remain in effect until the start of your next turn, although you must hold the axe to gain a bonus to AC from it.

Mental Fortitude.  While wielding the weapon, the bearer has resistance to psychic damage.

Psychic Power. The axe has 12 charges. While holding it, you can use an action to cast a spell from the list below.  Expend 1 or more charges equal to the level of the spell being cast, using your spell save DC:

The staff regains 1d6 + 4 expended charges daily after a long rest. If you expend the last charge, roll a d20. On a 1, the axe goes dormant for 1d4 days, losing all powers and becoming a +1 weapon until it recovers.