unless I’m forgetting something from an earlier page, this one seems kinda ambiguous. There are at least a few different ways of interpreting this, for example as Jordan Bai mentioned orichalcum might degrade over time, or Hijojo’s thoughts that it might be a type of magic or element that is incompatible with it.
Before you read the rest, it should go without saying that this is largely speculation.
Also, please be aware that it has been a long time since i read the whole comic, so there will be things that I have forgotten, or remember the general idea of but not the specifics.
One way I read this was with “dead orichalcum” being a different kind of orichalcum, or a recently discovered way of manipulating or configuring orichalcum, which doesn’t recharge automatically. Now, if I remember correctly, it was stated that orichalcum’s magical properties are based on it’s shape (I am likely wrong on the specifics here since it has been a very long time since i last saw where it was mentioned, it could have been physical as well and it might have been the way it’s refined or both refined and its shape), so they might have found a certain setup that causes it to not recharge naturally. Or dead orichalcum might be another material similar to the regular orichalcum but with different base or fundamental properties. If it’s the latter, It’s entirely reasonable that it wasn’t mentioned until now since it wouldn’t have been immediately obvious the moment magic returned like regular orichalcum was since it doesn’t charge back on it’s own.
Either way, if my base idea is is true, I think it would be highly likely for “dead orichalcum” to have other differences from the regular orichalcum in terms of properties, and I think we might have already seen it in use during the battle in Korea. It might have been the material used in the battery they captured the energy in, and used in the sword one of the girls was using. I think it might have been used there, at least in the weapon, because at one point it is mentioned that the sword is drained, though that does not mean it was dead orichalcum, just that it’s what got me thinking about it when I looked back at the battle after reading today’s page. There are many ways dead orichalcum might work to be used in those. It might actually be constantly recharging but at the same time releasing the energy faster than it takes it in, or it might not take any in on its own, but might be capable of hold much more at once and / or releasing larger amounts faster. Used in combination with regular orichalcum you might be able to better control those properties.
I’m led to believe that dead orichalcum is being used in devices and weapons because Toyoko brings this up right after mentioning a new device which means that dead orichalcum is involved in it. This page also seems to imply that the people designing this new device want Kate involved in some way, and I think this is related to Kate’s use of magic through crystals. Since they are making devices with it, and might have already used it in weapons, it’s entirely reasonable to speculate that they might be trying to create a device that heavily assists the casting of spells, maybe as a battery, or quite possibly by building the spell itself. If they can accomplish the latter, it would massively increase the amount of people who can use magic. It would be similar to the difference between a crossbow and a longbow. using a longbow effectively takes a lot of skill and training, thereby reducing the amount of people you can send to a battle with it, but a crossbow reduces the skills needed to mostly aiming and familiarity with the specific crossbow (eg, some of the things bows need you to learn and practice are how to hold the line, pull it back to the same position consistently, hold the proper form, release the arrow smoothly, etc, while crossbows eliminate the need for training most of those). If so, they probably want her to help them with designing it to meet the needs.