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
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I said there was a RIFT of light. which was SHOWN in the mission where you try to find Saint-14, where you end up opening said rift. Hell, you have to fight off Vex after you do!