Is this homebrew sword of wind control based on "Grasscutter" overpowered?

Question

I'm not the best when it comes to homebrewing magical weapons but I really want this to be in 5e. There is a sword from japanese mythology called Ame-no-urakumo-no-Tsurugi (天叢雲剣, "Sword of Gathering Clouds of Heaven") which was then later called Kusanagi-no-Tsurugi ("Grasscutter").

It is a sword that controls the wind, presumably by slashing at the air to direct a strong blow of wind.

History

In the legend Susanoo-No-Mikoto, the storm god, discovers it in the belly of the eight-headed snake Orochi, then through happen stance, it finds itself in the possession of prince Yamato who while on a hunting trip is betrayed by a local warlord who lights the grass around Yamato on fire in hope to kill him in what seems like an accident, Yamato sees he's trapped by the fire and starts cutting the grass around him to remove the fuel and that's when he finds out the sword can control the wind so using his trusty fire starters and his newly discovered magic sword Prince Yamato blows fire back at the would-be assassins, assassinating them instead.

Currently my design is...

Grasscutter

Weapon (longsword) , very rare This yellow bladed saber with a green hilt can control the wind, sending a gush of strong wind in the direction of the strike of the sword.

As an action, a slash of this sword sends a 60 foot cone of wind in any desired direction. Any creature inside this cone must make a DC 12 strength saving throw being pushed back 20 feet and falling prone on a failure and just falling prone on a success. This pushes fire out of the cone's area unless it hits a wall, in which case it snuffs out. It also disperses fog. Air elementals and other non-corporeal creatures have disadvantage on this saving throw.

As such it has the following properties:

• It can be used as a reaction to give disadvantage on an attack roll with a ranged or thrown weapon attack.
• As an action, it can blow sand, dirt or snow in a creature's direction in a 30-foot cone that persists for 1 minute. All creature inside the affected area have disadvantage on Wisdom(Perception) checks that involve sight and a disadvantage on their attack rolls.
• It can increase the speed of a sailing ship by 2 miles per hour.

It doesn't work underground or anywhere where "wind" would not usually be.

I fear this item might be OP, want this to be on-par with a very rare item, as this is meant as a reward for a party of 5 level 10 players by killing the end boss (which is a dragon, further connecting it to the myth), Can someone please tell me if this weapon is overpowered, underpowered or not explained well enough?

Answer 1

Is it overpowered? As you've written it, perhaps.. but only because you worded one of your abilities to always knock something prone, this is problematic.

If a character passes a save you can't and shouldn't knock them prone. This is bad design as a save should let the character in question avoid the worst parts of an effect. In this instance, the lesser of two evils (this being the knockback effect) would likely be applied, perhaps in a smaller denomination compared to a failure. Perhaps something along the lines of "Prone and 20ft knockback on a failure" and "10ft knockback on a success". This is fair enough for your PCs to come up with some creative uses for it (ship combat comes to mind) and if its turned against them they'll likely still feel that it's fair enough (aka I'm further away but at least I'm not prone.)

Generally, to determine if something is overpowered, we have to gauge it against something else already that already exists within the scope of the game and evaluate the merits based on something similar.

So currently you have:

• An effect that knocks a character backwards and prone on a failed save.
• An effect that gives characters using ranged attacks disadvantage.
• An effect that creates an area that gives things inside it disadvantage on perception rolls.
• An effect that makes ships move faster due to controlling wind.

Currently the closest spells to emulate these effects are:

• Grease + Gust of Wind ( A first level conjuration spell, a second level evocation spell )
• Blur ( A second level illusion spell)
• Fog Cloud ( A first level conjuration spell )
• Control Wind ( A fifth level transmutation )

These are all things a ninth level wizard would be able to do without any trouble with better effectiveness. If you removed the last effect, A third level wizard would be able to duplicate the effectiveness of this weapon.

If you want it to be more balanced. Amp it up some but remove the auto-prone. Give the weapon an enchantment bonus, and ten charges that refresh daily after a long-rest. Make the first level effects cost one charge, the second level effect cost two charges, and the fifth level effect cost five charges to limit how much you can do with it per day.

Also, Since the DC12 is a pretty low and very easy save to beat at tenth level for most things, you could make it so that for every three charges you use you could increase the save DC of the weapon's prone / knockback effect by one, which would bring the save up to around DC15 if you were in a pinch and needed to burn the charges to get something away from someone / knock someone down.

As a balancing mechanism you could even go so far as to have the weapon lose its enchantment bonus for the day if all of its charges are consumed.

So as far as the weapon goes, here's a general Stat block:

Kusanagi no Tsurugi

Weapon(longsword +1), Very Rare 10/10 charges

This yellow bladed saber with a green hilt can control the wind, sending a gush of strong wind in the direction of the strike of the sword. Kusanagi has a fine edge, tempered in the wind, and as long as the weapon is imbued with magical strength, it retains its +1 Enhancement bonus. When all of Kusanagi's charges are used, the weapon becomes a non-magical longsword until the user takes a long-rest in a place where wind is present.

As an action, when drawing this weapon from the sheath, a slash of this sword sends a 60 foot cone of wind in any desired direction. Any creature inside this cone must make a DC 12 strength saving throw being pushed back 20 feet and falling prone on a failed save or being pushed back 10 feet on a successful save. This pushes fire out of the cone's area unless it hits a wall, in which case it snuffs out. It also disperses fog. Air elementals and other non-corporeal creatures have disadvantage on this saving throw. (1 charge, +1DC/3 charges)

Kusanagi no Tsurugi can also create the following magical effects, provided the weapon has charges:

• It can be used as a reaction to give disadvantage on an attack roll with a ranged or thrown weapon attack. (2 charges)
• It can blow sand, dirt or snow in a creature's direction in a 30-foot cone that persists for a number of rounds based on the charges used. All creature inside the affected area have disadvantage on Wisdom(Perception) checks that involve sight and a disadvantage on their attack rolls. The user must be in a place with sand, dirt, or snow to use this ability and only one such cloud can be in effect at any time (1 charge / two rounds)
• When the blade is held aloft and the power of the wind the blade possesses is channeled It can increase the speed of a sailing ship by 2 miles per hour by channeling nearby gusts of wind to lift the sails. This power requires concentration. (2 charges)

Kusanagi no Tsurugi is a blade made of and forged by the wind, in places where no wind is present such as deep underground or underwater, the charges of the weapon cannot be used.

Answer 2

Your item is incredibly broken

This weapon is essentially multiple wands with infinite uses wrapped within a (magical?) longsword.

For the cost of 1 action within the 60' cone, you can:

1. Knock all creatures of any size prone without save
2. Push all creatures of any size 20 ft with save
3. Dispels fog
4. Gives disadvantage to saves for air elementals and non-corporeal creatures
5. Move/extinguish fires

As someone who loves, loves, loves to cheese, I can tell you that this item is incredibly broken.

If you knock a flying creature prone, it will fall. So if you use your "main" ability on that creature, even if it is an Ancient Red Dragon that is CR24, and even if it uses its legendary resistance, it will still be knocked prone and fall to earth.

You can knock a Tarrasque prone, with a single action! You can blow away a band of 78 medium sized mooks 20ft - for a single action! Over and over and over again!

You have effects that are similar to but more powerful than Control Winds, a level 5 spell that requires concentration, and all you need to spend is 1 action.

Further, for only the cost of a reaction you can impose disadvantage on an attack roll... spellcasters would require spell slots (and concentration) to do something like this.

As another action you can also cast Fog Cloud! Without need for spell slots or concentration!

Compare your "Very Rare" weapon to a Legendary weapon, the Holy Avenger:

Holy Avenger Requires Attunement by a Paladin

You gain a +3 bonus to Attack and Damage Rolls made with this Magic Weapon. When you hit a fiend or an Undead with it, that creature takes an extra 2d10 radiant damage.

While you hold the drawn sword, it creates an aura in a 10-foot radius around you. You and all creatures friendly to you in the aura have advantage on saving throws against Spells and other magical effects. If you have 17 or more levels in the Paladin class, the radius of the aura increases to 30 feet.

or the Vorpal Sword

Vorpal Sword +3

When you attack a creature that has at least one head with this weapon and roll a 20 on the attack roll, you cut off one of the creature's heads. The creature dies if it can't survive without the lost head. A creature is immune to this effect if it is immune to slashing damage, doesn't have or need a head, has legendary actions, or the GM decides that the creature is too big for its head to be cut off with this weapon. Such a creature instead takes an extra 6d8 slashing damage from the hit.

Do you see how tame existing legendary weapons are in comparison to your "Very Rare" Grasscutter?

To prevent abuse

Abilities should be more limited and focused

This sword has too many good options with no drawbacks. It is the Mary-Sue of swords. The ability to knock-down any creature within a 60ft cone for 1 action is also too strong and should be toned down.

It would also be unfair to other PCs who aren't wielding this sword that have to spend their very limited resources to achieve lesser effects. Think about how you sessions would be like if there's one player with an item that makes control spells and abilities obsolete - that player is going to overshadow the rest at the table. It becomes "that guy's" game.

This item should have limited uses.

Attach a (Recharge X-X) mechanic, charges per day or X uses until next short or long rest.

If you are DMing a large encounter and one of your players can force creatures in wide swaths of the map to roll saves every single round AND be pushed around, your game is going to slow to a crawl.

It shouldn't overlap other classes' features too much

The Grasscutter's multiple spell like effects is comparable to giving the wielder free dips into a spellcaster's features. Suddenly with the Grasscutter, a Barbarian is able to unleash an array of spell effects normally reserved for a level 9 wizard! While it is not exactly the same as giving the wielder 9 free wizard levels, the boon granted by magic items should not have this much latitude.

Here is what I suggest:

Grasscutter +2 (Longsword)

As an action you strike the air with the Grasscutter causing a mighty gale to emanate in a 60 ft cone in front of you. Each Creature Large or smaller within the cone must make a DC15 Strength saving throw or be pushed back 20 ft and be knocked prone. If that creature is an air elemental, it rolls its save with disadvantage. Non-magical fog within the cone is also dispersed. You may use this feature again at the end of your next short or long rest.

As a reaction up to two times until your next long rest, you may impose disadvantage on a creature making a ranged attack that you can see within 60 ft from you until the end of its current turn.

Keep it simple, don't let this weapon do too many things

I suggest looking up existing VERY RARE items on D&D Beyond and using those as templates. The Staff of Thunder and Lightning is a good example of a balanced and versatile magic weapon. You will find that items listed there do not come close in terms of ability powers and latitude in comparison to the Grasscutter.