Hey so I decided to take a crack at remaking your Uni statblock, for fun, because I like making statblocks anyways.
(I hope this is cool with you
@CrackerVolley, sorry if it is unwanted). I added in the Box Dweller and Fortify traits to try to bump it up in terms of CR, mathematically this is still a CR 4 but with abilities I think it becomes a reasonable 6. While doing this, I ran into a bunch of my old statblocks I made for my campaigns, so uh. Sharing those too, for the interested:
Klaus the Child Butcher: Santa Claus themed boss fight for a series of Christmas one-shots I ran. They ended up running away rather than fighting him, the cowards. This mini-campaign had the most spectacularly awful ending imaginable, in a good way. The players, entirely accidentally, damned an entire country to ruin and regression for hundreds, possibly thousands of years: they sent the poor bastards to the dark ages. Klaus here was meant to be an extremely formidable fight for the party (level 6, all, but also mostly comprised of experienced players with reasonably powerful builds), that allowed for some summoning from past parties who were related to the campaign (their characters had been sent to Hell, into Klaus' domain, and could have been resurrected/called upon by a mechanic in the fight if figured out). Klaus, for his part, had two allies with him: a substantially upgraded Bearded Devil that served as his bodyguard and captain, and a member of another infernal enclave that was there to negotiate a pact between the two- these guys were CR 6 and 7 respectively.
The Avatar: Another non-serious entry in the statblock repository, one of many creatures drawn up for the Halloween one-shots I ran for a couple years. This guy is Freddy Krueger, written as an illusory devil bound to a pirate ship by the name of the Wicked Smile. He was called upon to defend the ship against the party, and pulled them all into a modern factory setting filled with other slasher villains (Chucky or the Doll, Jason Vorhees or the Curse, The Creeper, Michael Myers or the Shape, and Leatherface or the Face)- the ultimate fight against the Avatar itself began with one of the party members, who was secretly a skeleton, being run over by a shipping truck slamming him into the wall just outside the arena, and ended with another of the party members being cast into the literal gate of hell that was being opened on the floor. Some survived, and in the real world learned that in all this fighting they'd actually killed the sole crew member of the Wicked Smile, so two of them decided to take the ship and become pirates while the moral compass of the party left and went through the cargo they'd left ashore... which was mostly silver. So he got fairly rich. Both the Avatar and Klaus were made in 2023.
Nightseed: A giant flying ooze creature I updated from 3.5e as a summon for a magic item I'd made for my players in the Spelljammer game I ran. I like him. He's cool. I think they only used him once because it was progressively riskier to use the summons from the magic item the more powerful they were. This was made in 2022.
The Governor's Gargoyles: A mini-boss fight consisting of three of these guys: one would activate first and, when destroyed, the other two would awaken. These were also from the Spelljammer game I ran, enormous statues erected outside of a mansion left on a desolate and transitory moon the party was exploring for elaborate reasons too complicated to explain here seamlessly. They were going to be these massive winged statues with corrupted plant life growing into them, wielding great glaives of tainted white stone. The party managed to completely sidestep this fight, they never got used. Also a 2022 creation. As was...
The Old Lord Governor: ...the Governor himself. Rad ******* boss fight with this guy, initiated exactly how I had wanted. After defeating a cult that was gathering in the ruined mansion, the party found a long since mummified corpse in a simple throne with a grand, golden staff plunged straight through his chest. So. The rogue took it, and the Governor grabbed him by the wrist and stopped him. Initiate fight. The remnant of a long dead and only sparingly referred to civilization that inhabited the moon, the Governor has tons of lore... that they didn't read. Such is life. Using his staff, he disintegrated two party members over the course of the fight: Tremendant, their Giff navigation officer NPC who was a character originating from an earlier campaign some of them had been in, and Jar-Brawn, the party's Hadozee druid. When he died, he exploded, destroying the Weave per his Fray the Weave ability. I loved this fight sincerely, it drew up the tension a shitload.
Astel, Naturalborn of the Void: One of the many conversions I made for Elden Ring when it came out. I think I have about 40 of them, ranging from fodder enemies to guys like this and Morgott. I intended to do them all, but I never got around to it and other people who get paid for this sort of thing on Patreon ended up doing it faster than me. Oh well.
The Crimson Queen: Made this while never intending to run it. There was a homebrew contest being run for Valentine's Day in 2022, I entered this: a fey noble clad in red that used love and enchantment to make her way in the world, brutally manipulating others to advance herself. For what it's worth, I won first place in that competition. No reward involved, but as it was a matter of votes, it made my heart warm.
Gryla and the Yule Cat: Another challenge in the same group of RPG people, this one for Winter in 2021. I used old Icelandic myths as a basis for these, I converted the two figures into D&D terms is all, really. Gryla is the mother of a giant clan who owns the Yule Cat, a gargantuan cat who eats people on Christmas who didn't wear the clothes they received. There's more to it than that, of course, look it up if it interests you. I did actually end up using these guys for the Christmas mini-campaign, with Gryla's sons and husband also ending up being statted (each son being a base template statblock with unique abilities added on per their quirks; each of them had one). You could consider these two the first bosses in the set of three leading up to Klaus the Child Butcher (the second, Arnkatla, wasn't particularly unique: a Snow Hag upgraded to be an appropriate challenge to the party and given Infernal minions, little else).
Fenrick the Great Deceiver: A bossfight from my first 5e campaigns, in 2021. A revenant trapped within a battlefield catacomb system called Grimfall, Fenrick had little lore implications other than he was a rogue caught amidst the armies and when he was resurrected as an undead by the curse that befell the battlefield, the remaining tenders of the crypt created an entirely mirrored room to restrain him in. The party opened it up and fought him. It was a good time. I really didn't expect any of the party members to figure out The Other World, but the one who got sent in remarkably got it very quickly.
Eschaton: ...all the way back in 2020, I was trying to write up a new monster a day for a few months. Eschaton was the culmination of a series of monsters, quasi-religious idols wrent into aberrant forms resulting in this, an ever-spreading biological apocalypse that consumed the earth beneath it to fuel its incessant expansion. I have never intended to actually run anything with Eschaton, nor his Saints and Apostles and Ministers (who ranged from CR 3 to 13). The idea I had in mind was mostly inspired by Ragnorra, from actual D&D, but upscaled to allow him to eventually consume an entire world, only to crash into the next and begin the next bout of anti-divine interference. I was running my original 5e campaigns at the time of writing, I think they were about level 6, so I wanted something crazy to work on.
That's all from the random pickings of the vault, a lot of it was just random media characters I converted into 5e upon requests (Doomslayer, Satoru Gojo, the Amongus Imposter, Steve from Minecraft, etc), these probably aren't my proudest work but they are ones I like.