I finally nailed down, after leveling up here and there past few days, and finished this one not too long ago tonight.
That last battle is so epic, it ain't funny. Level 18 and I was able to put it away -- and not easily, either. Only 2 party members were left standing.
You're given the option, after you finish the Main Quest, To Retire or Keep On Going. I should note -- you can Retire at anytime you want, if you so want, to get whatever Ending(s) you've earned.
The ending(s) -- once you agree to Retire -- are LONG and epic. I love these kind of endings, as your decisions in the game have an impact on what ending(s) you receive at the endgame screens.
Cohort SPOILERS
[spoiler]Also, it matters what Cohorts you had found along the way, as it tells you how certain ones ended up, if you found them.[/spoiler]
LORE Spoilers (for those with High LORE Skills)
[spoiler]
If you're LORE Skill is high enough, after you receive your earned ending(s) and all, you are given another option -- you can say to the ending section's narrator Volo -- "Wait! That's not how it ending! I'll tell you how it happened..."
And you can basically make all the choices right here on the fly right here at the very end (instead of in the entire game) and see all the ending options and decide which ones you want to see and everything instead of replaying the game and trying to earn them! LOL!
Awesome.
[/spoiler]