Ashbringer / Frostmourne, Just for Fun

[Oramac]

With World of Warcraft: Legion released, I got to thinking, how would I make the Ashbringer for D&D 5e? The obvious follow up to that is how to make Frostmourne.

So how would you make them? For reference, here's some history of the two swords: Ashbringer (http://wowwiki.wikia.com/wiki/Ashbringer) Frostmourne (http://wowwiki.wikia.com/wiki/Frostmourne)

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Ashbringer
Type: Greatsword (Legendary)
Damage: 2d8 Radiant

This +3 greatsword is imbued with the power of the Holy Light. It has the same features as a Holy Avenger, plus those listed below.

Ashbringer deals Radiant damage, and ignores resistance and immunity to Radiant damage.

When you hit an Undead or Demon creature of CR 6 or lower, that creature must make a DC 15 Constitution saving throw or be turned immediately to ash. (CR and DC might need adjustment)

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Frostmourne
Type: Greatsword (Legendary)
Damage: 2d6 Slashing + 1d6 Necrotic

This +3 greatsword is always cold to the touch. At the beginning of each dawn, the wielder must make a DC 20 Wisdom saving throw. On a failed save, the wielder's soul is trapped forever in the blade, and they may use the features below:

You may use an action to see through the sword, so long as it is on the same plane of existence.

When you kill a creature using this weapon, the creature must make a DC 20 Wisdom saving throw or have its soul irreversibly bound to the sword. You gain all knowledge, skills, and languages that the creature possessed.

[PeteNutButter]

A common tactic is to take existing magic weapons like flame tongue and add or modify them.

[EvilAnagram]

Frostmourne:
+2 Longsword, +2d6 necrotic
Wielder heals HP equal to necrotic damage dealt
Target must attempt Con save, DC 13 v. one turn weakened
Curse: On attuning to this sword, the wielder becomes cursed and must obey the commands of the Lich King. The Lich King shares a psychic link with the wielder through which they may communicate.

Edit: Ashbringer honestly just seems like a Flametongue greatsword.

[CursedRhubarb]

Ashbringer:
+2 greatsword, +1d6 radiant. Demons, devils, fiends, and undead take an additional 1d6 radiant. On a crit, If target has 75hp or less must make a DC 13 con save or be turned to ash as if by a disintegrate spell.

The previous Frostmourne looks great, I'd just add: creatures killed by this weapon have their soul absorbed into the blade and can not be returned to life by any means while the weapon remains intact.

[JackPhoenix]

Frostmourne: Blackrazor with changed fluff, fitting, as both are expies of Stormbringer.

Ashbringer: Holy Avenger. Add the abilities from Mace of Disruption for extra undead destroying action.

At least that's what I use for Warcraft game, because I'm lazy to create my own stuff. The Lich King is slightly modified Orcus from PotA, for example.