Hammer of the Thundersmith

Hammer of the Thundersmith
Weapon (warhammer), legendary (requires attunement)

When you hit with an attack using this magic warhammer, the target takes an extra 1d6 thunder damage. If the creature is made of metal or wearing metal armor, you can force the creature to make a DC 17 Constitution saving throw. On a failure, the thunderous blow reverberates throughout the metal and disrupts the creature’s actions. The creature is deafened and has disadvantage on attack rolls and ability checks until the end of your next turn. If a creature already under this effect fails the saving throw a second time, it also becomes stunned for the duration.

This hammer allows you to forge creatures of elemental air, such as air elementals and invisible stalkers. If you provide 200 gp worth of tin for each point of the intended creature’s CR (e.g. tin worth 1,000 gp is required to create a CR 5 air elemental), and forge it for 1 hour with this hammer, make a DC 17 Strength (Smith’s Tools) check. On a success, the tin sublimates into the intended creature. On a failure, the tin is destroyed and the process fails. If you attempt to create a creature with a CR greater than half of your player level (rounded down), the process fails. A creature created using this hammer is an ally to you and your companions. It obeys your verbal commands (no action required by you) and undergoes any task you give it to the best of its abilities. It remains under your control for 1 year, after which point it gains the freedom to act however it desires. It may seek revenge against its creator for subjecting it to a year of servitude, ally itself with those who showed it compassion, or vanish from the material plane altogether. The creature disappears if it drops to 0 hit points. You can maintain control over a number of forged creatures equal to half your proficiency bonus (rounded down) at the same time. For each creature created by this hammer that is currently under your control, the DC to create a new creature increases by 1, and additional tin worth 1,000 gp is consumed by the process.

This mighty hammer is a relic from the thundersmiths of yore, who forged an army of roaring wind for their stormlord lieges. The stormlords swept the land with elemental force, toppling kingdoms and reshaping the continent in a ferocious gale before vanishing all at once.

As the smith worked the tin, it began to grow softer, almost pillowy and lighter in color. It ballooned outwards in size, and rippled when struck, as if a condensed bubble of air grew inside of the ingot. Within minutes of working it, the metal seemed to become translucent and bounce on the anvil with each blow. Undaunted by this bizarre transformation, the smith continued to strike the tin, calculating each hammerblow with mysterious intent. As if an invisible reaction had reached its climax, the tin expanded suddenly. The smith stepped back and jammed a finger in each ear. The nearly invisible balloon of tin lifted off of the anvil and hovered for a second before bursting tremendously. From within, a being of whipping wind and cloud emerged: the process was complete.

Errata- Increased rarity to Legendary and DCs from 16 to 17