Helios Spear

Weapon (spear), legendary (requires attunement)

This spear radiates with warmth, as if it had been left in the sun. You gain a +1 bonus to attack and damage rolls made with this magic weapon, or +2 if you're in sunlight. On a hit, the weapon deals an extra 1d10 radiant damage. Whenever you roll radiant damage for the spear and roll a 10 on the die, the target of the attack must also make a DC 17 Constitution saving throw. On a failed save, the target is blinded until the start of your next turn. On a success, it's immune to this effect until the start of your next turn.

The spear glows with light while in flight. The first time on each of your turns that you hit a target hit with the thrown spear, that target takes an extra 3d10 radiant damage from the attack, instead of an extra 1d10 radiant damage. Making an attack at long range with the spear doesn't impose disadvantage on the attack roll. In addition, you can use a bonus action to magically teleport the spear to your empty hand, provided it's on the same plane of existence as you. When you do, it reappears in your hand in an instantaneous flash of light. When it emits light, the spear sheds bright light in a 20-foot radius and dim light for an additional 20 feet.

Sunbeam. You can use an action to throw the spear and speak its command word. When you do, you duplicate the effects of the sunbeam spell (save DC 17), and the spear immediately vanishes amidst the beam of light. This version of the spell is instantaneous and doesn't require concentration. The spear then reappears in your hand at the end of the spell. Once used, this property of the spear can't be used again until the next dawn.

And so he drew forth sunlight, folding it hundreds and thousands of times over. From this pure light, bound upon itself 'til hard as steel, he forged a weapon fit at last to strike against the darkness.