I just spent the last couple weeks re reading skin game and starting thinking about this series again, got a random theory and decided to post it here, more or less as proof that it’s something I thought of if it becomes true.

Harry will eventually power up, we know that, and I think he will end up creating his own mantle.

The first step was ignoring and fighting off the Coins temptation, it was training to allow him to stay free of the WK influence. We know that harry changes things, like at this point, basically everything he’s involved with. I think he will eventually change the Wk mantle (and maybe even winter, side theory not for here). This will be step two.

Step three will be him realizing that soul fire wasn’t given to him to combat the fallen, but instead to create, just as it was used to create the iverse. He will use WK mantle and the power at demon reach as building material for the new mantle and the tool he’ll use to forge it is soul fire.

Here’s the catch, he would have to not use all his soul fire, or figure a way to use it without depleting it. Doing so would shed his soul and he would only be left with the mantle in its place, making him not human and a slave to whatever his new purpose is. With a soul, he’d have all the power of a god, and all the free will of a mortal.

It’s the only way that really makes sense for him to stay harry, but be able to take on what he will face. Remember he’s fighting outsiders now, and the walkers can go toe to toe with Mab, but they are only knights, servants of more powerful beings. He’s going to need some serious power to do that, a dark hallow on demon reach would provide it, but he’d have to change the nature of the power and create something new from it to not succumb to the evil in it.

Side theory:
I’d be willing to bet that a lot of the other mantles were made in a very similar way, he have a WOJ saying that humans created the mantle of Hecate/Queens. It would be a mechanic that makes sense and explains the lack of a soul in them.