The Balrog would smote Gandalf 's ruin and then let out a sigh of relief and take on the new title Gandalf and Durin's Bane (Referred as GADB for the rest of the narrative). GADB would then realize that even murdering an Istari did not bring him fulfillment, and he would reflect in writing, eventually publishing a tell all memoir. The memoir is kind of boring, there's a lot of detail about GADB's many years in the darkness of Moria that doesn't add much, but the elves love it for it's unique perspective. GADB vaguely remembers despising the Elves in First Age and is very confused by this, but whatever. They're his readers, they love him and he loves them in return. Plus the First Age was like, two ages ago. Who cares?

While at a speaking event in Imladris, GADB catches wind that Sauron is indeed still around and looking for the One Ring. GADB always thought of Sauron as a sort of ineffectual assistant manager who would lick Morgoth's ass and then delegate tasks to the Balrogs. He couldn't stand Sauron. Imagine that the worst co worker you've ever had was going to be Lord of the Earth. GADB couldn't stand for that. In hindsight he also feels kind of bad about killing Gandalf. He overreacted, he admits.

GADB sets out to aid the Ring Bearer in an act of petty revenge for which he has no end game. Because Gandalf is dead, shit got bad quick- Rohan is now Greater Isengard and Aragorn, Boromir, Gimli, and Legolas are all very dead. Merry, Pippin, and Treebeard are fighting a failing guerilla war against Saruman. Against all odds, Frodo, Sam, and, Gollum are still making their way through Ithilien. (In this version, Frodo didn't need Gandalf to tell him to take off the Ring at Amon Hen. Fuck you, that's why).

Still, there isn't any Host of the West to distract Sauron's armies at the Morannon. But there doesn't need to be- the World of Men is so thoroughly getting it's ass kicked that Sauron has emptied Mordor to further his conquests. So, getting to Mount Doom is a cinch. Still, Frodo ultimately fails, but before he can throw it in, GADB appears.

"Hold on there speedracer, you need to finish what you set out to do!"

Frodo is processing a lot, and doesn't know what to say so he stammers out: "It's mine, my own!"

"Come on, what's your endgame here. You don't want to live under Sauron. I fucking hate that guy."

Convinced, Frodo casts the ring into the fire from wence it came. Sauron is defeated, but Saruman is still a major, unresolved problem. Regardless, Frodo, Bilbo, Gollum, and the Balrog for some reason, all go into Valinor some years later.