Ceremonial Macuahuitl

Weapon (greatsword or longsword), rare (requires attunement by a creature with a Strength of 16 or higher)
  Unlike the traditional, functional macuahuitls, this exceptionally heavy specimen replaces wood and bone with gold and jade. Used for ritual sacrifice, this weapon retains the magic bestowed by years of appeasing the sun gods. You gain a +1 bonus to attack and damage rolls made with this magic weapon. Once you use the ‘Eclipse!’ or the ‘Might of the Sun God’ feature, you can’t use that property again until the following dawn.
  Eclipse! While you hold the drawn sword in the sunlight, you can use an action to cast the darkness spell.
  Might of the Sun God. While under the night sky, or when you are standing in non-magical darkness, you can use an action to call upon the help of the sun god, casting the sunbeam spell (save DC 15).
  Very rare variant: Increase the bonus to + 2 and the sunbeam save DC to 16
  Legendary variant: Increase the bonus to + 3 and the sunbeam save DC to 17. Add the daylight spell to Eclipse!; you can use the Eclipse! property at will.