You gain a +2 bonus to attack and damage rolls made with this sword, which appears to be made partially of mithral and partially of a mysterious, sun-like radiance. When you hit with an attack with this sword, the target takes an additional 1d10 radiant damage, or 2d10 if the target is a fiend or undead. You also have resistance to radiant damage while this sword is on your person.

Aura of the Sun. Shadows and darkness flee before the brilliant aura emitted by this sword. You can use a bonus action to cause the sword to stop emitting this aura, or to reactivate it. The aura extends 30 feet from you in all directions, but not through total cover. The aura is filled with bright light, which is sunlight. A creature hostile to you or your companions that starts its turn in the aura takes 2d6 radiant damage and must make a Constitution saving throw (save DC 17). On a failed save, the creature has disadvantage on attack rolls against you until the start of its next turn.

Radiant Lash. You can use a bonus action to speak Blazeguard's command word and cause its mithral to seemingly melt, extending into a whip. In this form, it retains all of its features and traits, but functions as a whip instead of a longsword. You can use another bonus action to speak its command word and cause it to coalesce back into its sword form.

Charges. Blazeguard has 10 charges, which can be used to fuel the features below. It regains 1d6 + 4 expended charges daily at dawn.

• Reactive Smite. When a creature within 30 feet of you is hit by an attack roll, you can use you reaction and spend 1 to 3 charges to deal 2d8 radiant damage to the attacker, plus 1d8 per charge spent beyond the first. A creature that takes this damage must also make a Constitution saving throw (save DC 17) or become blinded for 1 minute.
• Spells. While holding Blazeguard, you can use an action to expend some of its charges to cast one of the following spells from it: branding smite (2 charges), flame strike (5 charges), guardian of faith (4 charges), guiding bolt (one charge per spell level, up to 4th), and mass healing word (3 charges). You can also cast the sacred flame cantrip at will while holding this sword.

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Damage: Radiant, Damage: Radiant, Resistance: Radiant, Blinded, Damage, Debuff, Utility, Combat, Versatile, Sap