Is this homebrew version of Glassteel balanced?

Question

I am not sure why the spell was not included in 5e. It's mostly used for flavor and cool factor.

Glassteel

Artificer, Wizard, Bard (Forge Cleric?)

• Transmutation
• Level: 3
• Casting time: 1 minute
• Range: Touch
• Components: Glass to be transmuted
• Duration: 24 hours
• Saving Throw: none

This spell gives a glass or crystal object the strength and durability of steel. The Glassteel also becomes roughly the same weight as an item made of regular steel, within a few ounces. The spell can transmute up to 5lb of glass or crystal.

At Higher Levels. Every 2 spell slots above 3rd lv, you can increase the amount of material transformed by 5lbs. 10lbs using a 5th lv slot, 15lbs using a 7th, and 20lbs using a 9th lv slot. Using a 7th level slot or higher to cast the spell makes the duration permanent until dispelled.

Is this spell balanced compared to existing official material (not including UA)?

Answer 1

This spell has (almost) no mechanical benefit to balance

The only time that casting this spell would have any mechanical benefit would be when you needed an item made of steel and for some reason only had access to a glass version of that item. Given that such a glass item is at least as difficult and expensive to create or acquire as the steel version and is certainly much rarer in practice, casting this spell will likely never have any mechanical benefit. We typically evaluate "balance" by weighing the cost (in this case, a spell slot, and possibly a spell selection) against the benefit gained. But if the benefit is purely the subjective cool factor of having a glass weapon or tool that's functionally identical to an ordinary metal version, how can you balance the cost of a spell slot against that? It's certainly fine to have "flavor" spells, but without any significant mechanical benefit, there is nothing to balance, unless you have some other criterion you want to use to define balance.

A few existing spells and abilities are similar to this

For what it's worth, there are a couple of spells or other abilities with somewhat similar effects, which you might be able to use or adapt for your purposes. First, there is the druid cantrip Shillelagh, which buffs a single weapon at a time. One approach you could take is to have this spell be a cantrip that works similarly, being limited to a single glass item at a time.

Second, the wizard school of Transmutation includes the Major Transformation feature, which can (with some favorable DM rulings about relative mass and value of glass and steel objects) transmute a glass object to steel permanently. You could allow the ability to instead give the object the physical properties of steel while retaining the appearance of the original glass. While not RAW, this would be a purely flavor change to the ability as written.

There is also the warlock Pact of the Blade:

You can use your action to create a pact weapon in your empty hand. You can choose the form that this melee weapon takes each time you create it (see the Weapons section for weapon options).

The reference to the weapons section of the PHB makes it clear that choosing the "form" of the weapon means that you choose which kind of weapon you want to manifest. But most DMs will also allow the weapon's appearance to be customized, or base it on the nature of the warlock's patron, rather than have it simply manifest as a perfectly ordinary-looking weapon of the chosen type. So a glass-looking weapon that functions the same as a steel one is certainly within the realm of possibility here, given the right DM, and the right patron.

Answer 2

This is very weak for a 3rd level spell.

For a spell that's in the same tier as Fireball, Haste, and Blink, this is distinctly underwhelming. The only thing you're functionally doing is making an item be as good as a mundane steel implement; the benefit of having transparent steel seems unlikely to be particularly valuable, to me. As you said, it's mostly for the cool factor.

I would probably suggest making the duration Permanent, and giving this spell the Ritual tag, both of which contribute to making the spell "do it once and have a cool item" rather than something you need to maintain all the time. I'd probably add a small expensive material component that's consumed in the process to avoid making a permanent ritual version of the spell too disruptive to your game world (on the "why doesn't everyone have magic glassteel windows, then?" level). I'd suggest something like 10 gp-worth of diamond dust, if you wanted to go that direction.

Glassteel in prior editions

In the 3rd Edition "Races of Faerun" book, Glassteel effectively combined many of the properties that Mithral and Adamantine had in that edition -- like mithral, glassteel armor actually counted as a lower proficiency level, and like adamantine, it gave armor or weapons a nonmagical enhancement bonus. That made it a very valuable material, worth many thousands of GP per item.

Going back further, in 2nd Edition's Red Steel setting, the spell minor glassteel was very similar to what I suggested: while it was a whopping 5th level spell, it affects 5 lbs of glass a time, costs a 10-gp gemstone, and is permanent until dispelled. The resulting glassteel material is described as being as strong as steel but weighing half as much (so you can make a glassteel equivalent of up to a 10-lb steel item with a single casting). When used for a weapon, it counts as magical for the purpose of creatures who can only be hit by magic weapons, but doesn't have any other bonuses.

Answer 3

I think it is reasonably balanced. In AD&D 1e it was a 5th or 6th level spell, for no particular reason.

There are certainly uses for it -- unbreakable windows and glassware and such. I would probably have it scale +5lb per spellslot upcast, not just every two levels. I would probably set it up like Wall of Stone -- 1 action to cast, Duration 10 min (concentration), becomes "permanent until dispelled" if you maintain concentration for the entire duration.