You take the role of Morgott(Psst, make a persona with his name for ease of use), who in this continuity, decided to get off of his ass and actually help out the Lands Between. He was forced to strike down basically all but one Shardbearer, and the only other surviving Shardbearer was Rennala both due to her compliance with Morgott’s actions and because her restored sanity gave her a shot at yelling at Radagon/Marika.
Either way, he got the remaining shards of the Elden Ring and at the behest of Maliketh, Marika’s Shadow, who recognized the seal barring him from within the Erdtree, set the tree on fire. Melina chose to make an appearance for just that and burning accordingly.
He also found the counsel of Goldmask, who tragically gave his life to give Morgott the Mending Rune of Order.
But once he ascends to take the throne, felling both Radagon and the Elden Beast through an extreme mixture of his new power, bearing all of the Great Runes you know the drill, and luck. Just pure luck.
After somehow succeeding in both battles, Morgott used the Mending Rune of Order, completely restoring the Elden Ring and by extension his Mother and became Elden Lord.
Now she has to suffer the consequences of having one whose very existence she hated by way of circumstance being her husband.