Uhm, about the new final boss, are there special unlock conditions or is it enough if we beat the current final boss once?
Not going to be unlock conditions in the way you're thinking about it.
If you've played Isaac, it really is very similar to how the Hush, Boss Rush, Mega Satan, or Delirium work. On any given run, with certain conditions met, you then have the OPTION of going to one of those three places. You don't have to go to them, and can simply continue onwards towards the normal ending on the Chest or Dark Room. But if you think your build is good enough, you can give them a go.
It's going to be like that. And I'll warn you right now, the entire reason why it's going to like this is because this is meant to be a *very* difficult boss. It'll still be divided up into the different difficulty modes, but compared to other stuff on a given mode, it's going to be very tough. On Misery mode it's going to be outright ridiculous, because of course it will be... I don't have to be kind whatsoever on that mode. Not to mention that this thing will have what I'm calling "anti-rampage" mechanics to it on all modes... I'll leave how that works as a surprise (and I'm still testing it anyway), but it means nothing in the game will let you flatten it in 5 seconds, or anything like that. Dodge or die, here. You'll still want a decently powerful build for it, though. This is the only boss that will use such a thing, and the other half of the reason why it's optional. It's likely to be a long fight.
In other words, it's meant to be the game's greatest challenge, for those that want it. Specifically, *my* idea of this type of challenge. But those that don't want it, can just ignore it. No achievements for this guy, because I want this to be *completely* optional. I don't want another Delirium driving players up the wall because getting 100% of achievements requires doing absurd things against him. None of that crap here, thanks. There's no reason to get all frustrated and aggravated against this guy if it's not the sort of challenge you're after. Similarly, Misery mode will have no achievements either for that very reason.
As for what the conditions for reaching the horrid thing will be, that's undecided. What IS decided is that unlike the Hush, the entrance to this fight will appear at the very end, after Terminus is defeated. You can either go into it (if you've gotten it to open), or just end the run with a win. The choice is entirely yours. I expect most players will just end it normally.
I will say that actually making the thing is not exactly the most fun process in the world. I'd been dreading that particular task for awhile. Though maybe a little less irritating than trying to make the patterns for the Obscura ships in TLF. What with the turn-based combat and the giant bloated hitbox of the player's ship. I'm glad those came out well, but good grief, they were a total pain to make.
