I spent some time poking at Archipelago and I was able to put together a Hollow Knight/Subnautica randomizer in about 30 minutes. Spent a few hours playing it and guess what? These are both really huge games! I had never tried randomizing either before and the learning curve has been somewhat steep. HK is extremely limiting at first, since you need mobility options to make any real headway - the game is softlock city without the Mantis Claw, though thankfully you can choose to warp back to your most recent bench at will. Stag stations are mixed in with the random item pool, so I was able to get to the Resting Grounds and King's Station, but you can't do a whole lot in either of those areas without the double jump, air dash or wall climb. Combat hasn't been too big of a challenge so far, at least. I was able to clear out the three bosses in the Forgotten Crossroads, but I didn't get anything of note for my troubles, aside from the King's Brand (which won't be of use for a while yet).
That means that everything I need must be in Subnautica, right? The Subnautica rando seems to work by shuffling all the unlockable blueprints between the various PDAs and databoxes in the world (and also Hallownest, in my case). You don't find items lying the around in the world to scan like in the vanilla game, which cuts down on a lot of the searching you would normally do. You can choose to put blueprints behind creature scans, if you want to mix things up some more. And yes, that can include the leviathans if you really want to make your life difficult! I didn't choose that option, so progression mostly comes down to visiting story-relevant locations, grabbing the databoxes/PDAs and any rare resources, then moving on. It hasn't been too difficult so far, since there are a lot of places to check from the jump, but it's pretty slow going without the seaglide (one blueprint part was for sale at Sly's store in Dirtmouth, but the other still eludes me). The game also just straight up tells you where the nearest check is in the top left corner of the screen. I don't know if there's any way to turn this off, as it really breaks immersion, but it's probably a necessary evil if you don't want your run to last for 30 hours. It doesn't discriminate between checks you can actually get or not, so I found myself being pointed to some wrecks that I couldn't get into for lack of a laser cutter. The Aurora is radioactive from the get-go, so you can't immediately strip it for parts either.
I don't know if I'm going to keep going with this/these runs or not, since it really is a whole lot of game to work through by yourself. Hopefully I'll have a chance to try a proper multiworld with other people at some point, which will at least make the time pass more quickly when I'm slowly checking locations. I might also be better served by sticking to shorter games, because checking every location in Hollow Knight takes me about 10 hours on a good day and Subnautica is probably twice as long. Still, Archipelago is an extremely cool system and I'm excited to see more games added to it. Ever since I played SMZ3, I've wanted a version where you can mix and match other games - ActRaiser and MegaMan X always seemed like they'd be good candidates. In the meantime, I guess I can always fire up [checks list] Hylics 2 and A Short Hike?