This idea might be a bit blunt and straightforward, but it's better than nothing. Saint-14 had his light drained out, right? Well, why don't we just take his corpse and toss it into the rift full of his light?
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no, that's not how it works. there cannot be a "lake of his light" since his light was destroyed when it was drained and the lore tab of the perfect paradox implies that we will meet saint either in the past or future before he dies, but he has to die in order for his gun to be destroyed so we can reforge it