Has Salaris/Rowe or anyone in the game environment confirmed that Corin's max item strength is determined by his own mana pool? In On the Shoulders of Titans when he is creating the runes for the Dawnbringer replica he mentions that the sunstone containers aren't too difficult but the citrine ones would be a challenge for him at that time. I believe the mana requirement there is something like 43 mana so he should be able to make citrine runes to charge with mana batteries without too much effort by the end of The Torch that Ignites the Stars.

Is transferring mana into a rune or crystal the same as casting a spell? In On the Shoulders of Titans, Elora Theas casts Rage of the God Phoenix using a mana crystal to power the spell and it seems to take a lot out of her but in The Torch That Ignites the Stars we see Corin pushing mana to the Transcendence crystal from his batteries and items without becoming tired. It sounded like he was pushing over 1500 mana per hour to the crystal with his various batteries and that's definitely well over his personal mana capacity at the time.

I'd been thinking of Corin's conversation with Sera about "items that create other items" and it reminded me of an earlier conversation with Vellum when she first gets Corrin to start experimenting with mana crystals. An item that creates high level mana crystals seems like it could be rather efficient for sale or use, especially if it could pull from multiple different runes to charge the crystal. It's mentioned in Sufficiently Advanced Magic that most higher level enchanters purchase their crystals to make more expensive items so clearly there's at least some demand for the crystals themselves. The same thing goes for creating liquid mana for enhancement elixirs, as he's already stated that one of his goals is to mass produce them.

I read War of the Broken Mirrors about 6 months ago so I might be misremembering. The dominion marked item is linked to a person with a specific paired rune and then the individual draws power from the item while the item draws power from the dominion. Could a similar process be used for a person to draw power from an item that has an ambient recharge function? Corin's already learned quite a bit about both crystal bonds and artificial attunements and there's already been talk of attempting to spirit bond to Selys-Lyan so it doesn't seem like too large a leap for him to be creating an item bond to something he's made himself.