Psionblade

Weapon (any sword), uncommon (requires attunement)
  As locomotion in the astral plane is powered by thought, wayfarer’s of this vast, water-less sea tend to be of greater than normal intelligence. Hence it follows that their armaments should be manipulated by their greatest asset—thought itself—in place of the strength of their arm.
  While wielding this magic weapon, you can use your mind to manipulate and empower the blade. You can use your Intelligence for the attack and damage rolls of attacks using this weapon instead of Strength or Dexterity.
  Psionslice. While holding the weapon, you can use a bonus action to cause it to switch from an ethereal blade of nebulous energy that deals psychic damage on a hit, to a hardened, crystalline structure that deals slashing damage on a hit, or vice-versa