I'm at the end of the game, completed all quests in list, except for the 'threshold' quest, but only at level 8 in the Gold Dragon Mythic. I understand, for 'secret' ending, I have to be L10. Do I need to wait till I get the additional mythic quests so I can level up to L10 or is this like other quests - because I didn't talk to some minor NPC in Act III, I cannot progress to L10?

It looks like I should be getting the mythic quests from 'Halaseliax', but he is not in Drezen like he should be. Information on mythic upgrades seems to be all over the place and it is extremely easy to miss out on something because you picked the wrong conversation topic two acts ago or didn't remember to run around and talk to every NPC in every location every day.

You missed something, or it's a bug. When the threshold quest become available, if you have completed all the other mythic quest, your mythic level should be 9, the 10th is gained just before the last room in the game (i know it's stupid) after entering the last threshold fortress, but it seems you missed a quest, beside reloading, don't remember when at, or using toybox mod to force your level, there is nothing to be done at this point.

Inclined to believe it may have been a bug (though not discounting I missed something since it is too easy to do with this game). During the battle in Iz, after beating the big bad, right before he fell through the floor, the game sort of froze, similar to the other mythic increases, but didn't give me the increase. I did pick the gold dragon response there.

Unfortunately, I haven't been able to get Toybox to give me the next level (added it, but the gold dragon selection is unselectable, so can't complete the level up). Will play around a bit with it more to see if I can get it working, but at this point, my previous save is hours and hours before. I'm just going to wait for the DLCs and give it another go at that time.

At this point, I've had locations open up that I cant get out of, quests activated I can't complete and now my mythic selection not working for me. Hopefully these bugs will be fixed when the DLCs start dropping. Note, looking through the notes for 1.1 beta, not seeing fixes for the minor and major issues I've run into.

Toybox have an option to bypass any and all requirement for feat and classes, plus a button to force unlock all mythic path, selecting those may allow you to choose golden dragon regardless and finish the game

Without being an ass however, i must tell you that the golden dragon ending and decisions are basically non existent or irrelevant, a mythic path tacked on at the last moment, it most assuredly feel as much, maybe a future enhanced edition will fix that, they did somewhat allow you to not thanathos snap yourself out of existence with the aeon path with the last beta patch, so GD may still have hope.

Thanks, will try out the other options in ToyBox. Did manage to tank the laptop trying to mess around with etude's, got stuck in an infinite loop.

Understand, this is not a big deal in the overall scheme of things, but was trying hard to get to the 'secret ending' and need the L10 mythic path to complete. Makes me feel like I should have kept on with the Azata path, but switched when allowed (turning into a gold dragon was nice, but losing the dragon companion sucked).

Have waited (game time) for a few months already, waiting on Hal to show up with the additional mythic quests I believe I need to complete, but haven't gotten them. Running around in the world map to burn time and make sure I didn't miss anything, experienced Jubilost (not sure what to do with Gold Toad). Interestingly, saved Sevalros and started quest Brother in Shadow, which I cannot complete because Hal is not in Drezen. I believe that quest is later in the Hal quest lines and not the first one I've gotten out of order with the game as it stands now.

EDIT: Just FYI, the toybox experimental 'Ignore class and feat restrictions' level up option along with the party option to add +1 to my mythic level got me the Gold Dragon L9 (enabled Gold Dragon option so I could get to the next step). But when got the L10 in Threshold, had to enable the experimental option again in order for the mythic selection to be enabled. Something broke in the path. Maybe because I was still Chaotic Good rather than NG? Was able to get the secret ending, but had to wait almost a year in game for the right dates.