Aymr

Forged by Those Who Slither in The Dark to be used by the Flame Emperor in the fight against the Church of Seiros, the fanged Aymr stands as a symbol of the war. As this axe burns a path to a new future in the hands of the Empress, its burning red light terrifies all of those who stand in her way and sets the hopes of her enemies to flames. The fangs of this weapon will eventually tear apart those who created it, waiting to dish out the vengeance of the one who bares her fangs. Only then, when her vision is complete, with Aymr rest.

You gain a +3 bonus to attack and damage rolls made with this magic weapon. Aymr has the following additional properties:

Hero Relic's Toll. If you don't have a Crest feat, when you make an attack using this weapon, you take 1d12 necrotic damage. If this damage reduces you to 0 HP, you are transformed into a Black Beast. Your game statistics, alignment, and personality are replaced with the Black Beast’s. When you transform in this manner, you assume the hit points of your new form, and your gear (including this item) melds into your new form. This transformation lasts until you die or a creatures cast Greater Restoration targeting you. For the creatures casting of Greater Restoration to succeed, their Spell Save DC must be equal to or greater than 8 + your Constitution modifier + your Proficiency Bonus. This property is active even if you are not attuned to Aymr.

Magical Focus. You can use Aymr as a Spellcasting Focus while you wield it.

Umbral Steel Forged. Aymr can't be destroyed, have it's power removed, or have it's formed changed by any means.

Unstoppable. When you roll to hit a target creature with this weapon, you may ignore any bonus that creature has from armor or shields to determine if you hit the target.  

Bane of the Immaculate One. If you have the Crest of Flames feat, whenever you attack a dragon with this weapon, you deal an extra 2d10 slashing damage to the dragon.

Raging Storm. Once per long rest, you may channel your fiery rage and hatred and unleash it against your enemies. For this turn, whenever you deal damage to an opponent with this weapon, you may make a DC 12 Strength Check. If you succeed, you may make an additional action, bonus action, and movement this turn. For each Strength Check you would make with this effect this turn after the 1st check, the DC is increased by 4 (2nd activation would be DC 16, 3rd activation would be DC 20, etc).

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

Notes: Bonus: Magic, Damage: Slashing, Damage: Necrotic, creature with the Minor or Major Crest of Seiros feat, Versatile, Topple