Can the Opal of the Ild Rune gift of flame be given to a Pact blade?

Question

the Opal of the Ild Rune gift of flame can be transfered to a nonmagical item, a weapon, by tracing the ild rune there with your finger. The transfer takes 8 hours of work that requires the two items to be within 5 feet of each other. At the end, the opal is destroyed, and the rune appears in red on the chosen item, which gains a benefit based on its form:

Weapon. The weapon is now an uncommon magic weapon. It deals an extra 1d6 fire damage to any target it hits.

The pact of the blade states this "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). You are proficient with it while you wield it. This weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage."

the text states that it counts as magical but doesn't state that it IS magical, so my Question is this:

Can you apply the ild rune to a weapon created by the pact of the blade feature?

Answer 1

Maybe, but you shouldn't.

I don't think "will this work" is actually an important question. Even if this would work, it's a bad idea that will waste the rune.

Let us assume, for the sake of argument, that you unambiguously can use the Ild rune on your pact weapon. What are the implications of doing that? Well, your pact weapon isn't a single object that changes form -- that is, you can't apply the Ild rune to it and then have all the pact weapons you create forever after deal extra damage. You "create a pact weapon in your empty hand", and the weapon "disappears" if you create a new weapon, leave your weapon behind, dismiss it, or die.

Needless to say, you probably don't want to create a permanent magic item that disappears forever because you walked away from it.

You can use the Ild rune on a nonmagical weapon, then bind that now-magical weapon as your pact weapon, and that's fine, but applying the rune directly to your pact weapon is just a bad idea even if it were allowed by the rules.

Answer 2

Going by the logic in multiple answers to Pact of the Blade and Antimagic Fields, the answer is:

• Yes, if you're using the plain Pact of the Blade pact weapon, which is a supernatural, but not strictly magical ability
• Possibly no if you're using a weapon created with improvements from the Improved Pact Weapon invocation (where all products of Invocations are explicitly magical); the invocation wording doesn't actually say the weapon is magical, but it was produced thanks to a magical ability, so it's probably a magic weapon.
• Definitely no if you're using a weapon created with one of the UA Superior Pact Weapon or Ultimate Pact Weapon, both of which use the phrasing "the weapon counts as a magic weapon (with a +2 or +3 to attack/damage)" with no qualifications saying it's only for a specific purpose.

That said, how this works is entirely outside the detailed rules, so you'll need to discuss this with your DM. In particular:

1. When the pact weapon becomes a magic weapon (as a result of the rune being attached), must you perform the ritual to bind a magic weapon to you as a pact weapon?
2. If not, what happens when you banish the weapon and resummon it? Is it a new weapon each time, so the rune is lost? A really generous DM might let you resummon it with the same variable form normal pact weapons get, but the rules that exist make me think this would violate both letter and spirit of the rules (if you want to bind a magic weapon as your pact weapon, it's at the cost of losing mutable weapon form).

Frankly, the simplest solution is to just pay the trivial cost of a non-magic weapon, bind the rune to it, and perform the ritual to make it your pact weapon, and avoid all this ambiguity.