I've done most of the things in act 3 that there are to do, and now I've really only got two major story/plot threads left. Going after Gortash (which includes going to the irone throne and destroying the steel watch) and going to get the hammer from Hell and then (maybe) saving Orpheus. It feels like going to the iron throne will trigger an enemy relationship with Gortash, after which point I'll need to go straight after him, which to me seems like it will trigger whatever the endgame is. Is this true? Or can I go after the iron throne without immediately skipping to endgame? In my head my path of desire is do irone throne > destroy steel watch > kill gortash > go get the hammer > do endgame, but I'm afraid to start this sequence for fear of getting railroaded out of going to hell.
At what point does the endgame actually trigger? Is it an event? How much time do I get to wrap up before delving into the final areas?