Frostmourne, Variant (5e Equipment)
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Weapon (greatsword), legendary (requires attunement)
Frostmourne is a fearsome, rune-inscribed two-handed longsword of the Lich King. The runeblade originally belonged to Ner'zhul, who thrust it from the Frozen Throne, waiting for an adventure to discover it. Upon attuning to the blade the welder +4 to hit and 1d6 +5 damage, bonus damage of 1d4 against good-aligned beings, bonus damage against living beings (1d4), and a life-draining effect that heals its wielder whenever he deals damage (1d4 healing). The Runes itself simply mean "Soul devourer - The Cursed Blade of the Legion"
Soul Rending As you slay foes and consume their souls, the blade grows stronger. You can use up too 4 souls as an attack instead of swinging, you can cause up to 4 souls to come from the sword and attack, do 1d4 frost damage per soul, each must make its own attack.
Eternal Curse You must make a DC 20 Wisdom save at dusk every day to wield this weapon, and resist it's attack against your soul. On failure, you may have your alignment shifted to evil. However, you will stay lawful, neutral, or chaotic. Alternatively, you may take 1d12 necrotic damage, and keep your current alignment. Each time you resist your hitpoints will permanently be deceased, you'll regain the hitpoints by using a soul (3d6) or having the sword at least a mile away or by a remove curse or wish spell.