Give me your absolute best YGO x Fate headcanons

Ah gee since ya asked so nicely heres my convoluted crossover AU. Also this got hella long so I'll add a readmore

-the protags would all wind up at Chaldea due to being summoned by the godly powers within their own universes (Egyptian Gods, Crimson Dragon, etc.) and are tasked with helping them. Yugi is pre Ceremonial Duel (for Atem), the rest are from post series

-Gudas just so used to all the weirdness surrounding them so they take it in stride. Holmes on the other hand is losing it because he fears they may have been some type of dimensional collapse. He freaks out further when some of the kids say "oh yeah that happens all the time". Da Vinci sets them up to assist Guda since they can use magic (at least half of them use magic and the other half literally fuse with duel monsters) without needing magic circuits (which interests her GREATLY) so she introduces them as a set of new masters to help.

-their decks are still with them but now instead of being confined to the game they can actually summon them as Familiars/Phantasmals, though they can only support a few at a time.

-most, if not all servants are suspicious of these new masters (guda is my favorite master i dont need another one), but its only initial waryness since these are actual kids like Guda and they default to Parent Mode. Theyre even more surprised to learn about the exploits within their own worlds.

Now onto some of the dynamics:

-Yugi would just be happy to meet all these heroes from history. He understands the seriousness of the situation and despite his initial kickback he'd be onboard to help. Atem would take this opportunity to ask around to see if any of these ancient heroes would know him (since pre ceremonial duel he'd know who he is from Mem World). The Pharaohs (Ozy, Nito, Cleo) would be surprised about a Pharoah they've never met before, and especially his divinity since he could summon three Egyptian Gods to aid him. He was from 3000 years in the past so Egypt was beginning in its decline, so such a modern (relatively) Pharoah holding such power would shock them, though in the end Ozymandias would still declare him one of his friends and theyd get along. Yugi would leave the Puzzle with the Pharoahs so they could speak while he went around meeting a bunch of the heroes. He'd love to play with some of the kids though he has earned his fair share of ire since the King of Games never loses on Game Night, Poker Night, or any other type of games. Yugi has more supportive abilities in his skillset for the ourposes of battle, while Atem can more freely use his shadow magic since he's being supplied.

-Judai is more nonplussed than anything. He was already wandering the world so for him this is just another checkpoint. He finds the ability to summon his monsters as familiars more convebiant than anything since he could already speak to them. Many of the magic users are particularly interested in his ability to talk to spirits since its a rare ability in general and usually limited to one type of phantasmal, not to mention empathetic abilities on their own are somewhat unheard of in Nasuverse. Yubel is a protective force around him and for combat training scenarios shes extremely hard to get around since her deflection ability, while hard to maintain when Yubel uses her final form, is pretty much on par with Lord Camelot in terms of defense. He's generally friendly but comes off as rude sometimes due to his general nonchalance. Gets along especially well with some of the more volatile servants like Berserkers and Avengers since his empathetic abilities are soothing to them.

-Yusei is cautious and guarded here. He has responsibilities in his own world he'd want to get back too, but doesn't have it in him to just leave. His D-Wheel somehow came along (Yuya shivers in the distance) with him, so Da Vinci did the only reasonable thing upon seeing a miniature perpetual motion machine and tried to impound it immediately for study. Yusei was happy to share his info and skills on Momentum and implementing it into Chaldeas energy systems, something that had Tesla and Edison proud since one so young was already (but only barely) supassing AC and DC. Holmes was also extremely interested in Clear Mind and the Crimson Dragin, since Yusei managed to consolidate his own concentration into pure evolutionary energy and may have accidentally interacted with an elder god in the process (kinda like Holmes). Yusei assures him the Crimson Dragon isn't evil and that its called Quetzalcoatl, which has Fate Quetz coming in and asking about herself, further complicating Yusei's confusion on the Crimson Dragon. For combat, he starts off supportive by swarming his field with low power monsters before suddenly summoning a more powerful one. With Over Top Clear Mind they become even more powerful and evolve on their own, so Stardust can become Shooting, but summoning Quasar is very dangerous since its extremely powerful but taxxing.

-Yuma is absolutely excited. Astral not so much. "Astral these are literal HEROES how can you not be excited!?" "Idk probably the part where they'll kill us if we take a wrong step?". Yuma loves to hang around servants like Drake, Shiki and Beowulf, and loves swapping stories of their adventures. Abigail heard about aliens and wonders if Yog Soghoth is an alien, but Yuma tells her that the Astrals and Barians are not like Yog Soggoth, even if Don Thousand as described kinda sounds like him. Astral can be seen since since Heroic Spirits are consolidations of magic while Astral was basically an energy being of the same type, and does float through the halls, occasionally scaring someone by mistake. He does get along with a mysterious woman in a kimono who seems to appear in the twilight hours, but he cant ever really remember her face. In combat Astral and Yuma can do their usual combination form which causes their Numbers to automatically Rank Up upon summoning, the higher the form the further they can rank.

-Yuya has it a bit rough at first. He just got out of a war and now he was being dragged into another? Thankfully he gets his bearings quickly but is still somewhat shaken. Some of the servants are wary around him because they can feel the distortion that exists within his soul, his three other versions, and the power that could trun him into the Supreme King once again still exists there even if Zarc has passed on. He gets along with Siegfried well enough, and they swap stories about how the expectations of others can lead you to ruin. The Alter Egos feel a kinship to him since he's also a consolidated personality rather than a full person, though he gets along best with the Celts. Cu, Scathach and Fergus all love to see his performances, but to them that just meant that they can put him through warrior training especially after they hear about the war he went through. Scathach insists that him running for his life while she chases is good training, while Cu agrees while running alongside him. In battle he uses his acrobatic prowess enhanced with a little bit of fortification/protection magic, and can summon all four of his dragons to help him. Since the other Yu Boys are stuck within Yuya, they occasionally trade places:

Yuto gets along with Archer and occasionally helps him out. Archer is sympathetic to the struggles he unerwent in his own world and makes sure to keep his spirits up while also trying to ignore the irony.Yugo and David have struck up a strange friendship since they both have the issue of mistaking people for their so. David sees Yugo talk about how even if his life was hard it was worth it for the people he loved and remembers his son fondly.Yuri is generally avoided since even after the merge he's still something of a wildcard, but he gets along well with Hans and Kiara of all people. Sometimes he'd share the stories of the training he underwent in Academia, how the Professor trained him to see people as toys and all the people he's hurt, how his dragon was his only friend and how itd protect him, and Hans couldn't help but hate his pessimistic attitude in expecting this while Kiara wouldn't really care too much but also wouldn't insult him by offering condolences. He knows he's become a monster and he won't deny or forget his mistakes, he'll simply try to do better.

-[note: Vrains suddenly had its ending announced for Sept.25 (i believe it may have been cancelled) so based on the episode title of 120 Yusaku and Ai will reunite and thats what im following here] Yusaku is skittish at best, downright invisible at worst. He doesn't want to be found, and even some of the Assassin Class servants have trouble tracking him down when needed. Ai managed to bring along a spare SOLtis body with him so he can walk around and physically interact with Yusaku. Even if they still had some tension between them they still cared about each other so they would keep each other company. It got real awkward when BB first showed up talking about being a sentient AI, so Ai immediatelt tried to befriend her, only to learn about her inhuman nature. While Ai may dislike that aspect of her, he knows from what happened with Roboppy that you cant forcibly change what you are, so he does his best to try and get along, which infuriates BB to no end since she feels like she's being talked down to. Yusaku as a programmer helps with most of Chaldeas regular workforce and he accomplishes hiding in plain sight by being the only master to interact more with the regular work staff than their servants. That being said, it doesn't change how some like Tamamo or Suzuka try to drag him out so he can meet some of the other servants. He gets along well with Kerry. Likely because they barely speak and share E Rank Luck.