>>37485
Previously Medea was called a magus "infinitely close" to a True Magician with no further elaboration, though with the feats she showed and what other Casters have done subsequently she probably could not have taken on an Ultimate One even with backup. Currently it's...complicated, but no that is not actually the case. See, instead the thing about True Magic is that it fundamentally seems to run on different rules to everything else. And yes, a SUBSET of that is True Magic is not nerfed by science-but that's simply because True Magic is further back in the queue of shit humanity does not yet know how to replicate. Key emphasis,
yet.
Judging from Shiny Star and the Ether Cannon, True Magic is roughly comparable to Authority but within a more narrow but potent scope-which without a good understanding of a specific Magic, is kind of a short term tradeoff since Authority is already freeform enough that reasonably powerful gods and even some mages like Himiko can perform time travel. Arguably it is a net upgrade as a SYSTEM compared to Magecraft since even Goetia's goal was merely called "close" to the 5th Magic. But the thing is for performing magecraft, the caster matters as much if not more than the system. And that's why the likes of Kirsch, Pepe and (name a powerful god) still pack a greater punch in terms of raw power than Aoko is shown to currently.
>>37480
It's not really a buff accounting for Melty Blood stuff, but for one thing we've seen Arcuied-the weakened Arcuied-fuck with space and time to deflect the Seventh Holy Scripture and 2 million volt lightning magecraft. We also see her conjuring vines to restrain people and creating pathways; again not really a buff, except maybe in terms of finesse for her powers. Also Regression to the Age of the Gods is more clarified: It's a type of magic circuit that lets Arc reproduce Mysteries that existed before True Magic. So theoretically for example she could whip up an Earth-themed version of Ishtar's Venusian texture Holy Grail-empowering racing track. Presumably this is used to supplement her Marble Phantasm ability in OC3 to conjure up several "battle stages" where she makes you fight versions of your old enemies, and also why her Marble Phantasm NP explicitly send attacks from 1200 AD through space-time to blast people from a hard-to-defend dimension (time) like Altera's stolen Mars sword. In her natural non-Servant state, Archetype Earth at least is said to have a World Egg instead of a Saint Graph, something all Ultimate Ones apparently have in their normal state of being; this is apparently the thing that give her the backup powers.
The main thing is Arcueid's physical body is actually a kind of limiter. As long as she isn't otherwise mentally incapacitated, there's no limit on how much energy she can pull from the planet instead of just scaling up to people. This is the basis of her Lumina body: An End of Evangelion entity-like state where Arc is always as big as the biggest building created by the dominant civilisation, has the mass of the earth but only crushes manmade objects instead of natural territory, paralyses people instantly with her, kind of naturally terraforms the world into a hostile primal state just by existing, can only be wounded by attacks that hurt her (and heals rapidly even from most of those. Naturally, the MEoDPs still work) and the state of this body is described as simultaneously hard, smooth, and a microcosm of the Big Bang. Also if you jump into it with a sufficiently strong attack, you can see a hologram of the Big Bang in her soul. It's...look, I'll just post this link here. Suffice to say that falling into Arc in this state is entering a trippy dimension where time is dead and meaning has no meaning, which is sorta like a Ploy Kickshaw++++ in the sense that it's a magically created "virtual" universe but with more tangible consequences than a mere hologram, and according to Roa Arcuied's heart is the beginning and end of a universe, the atomic structure of all creation, and the location of Eternity:
https://forums.nrvnqsr.com/showthread.php/9651-The-Celestial-Egg
(As a side note I think the fact that a heartless ORT just effortlessly stepped on Ixquic, who is more or less a dinosaur-shaped TsukiRe Arcuied, is unironically why Gohanposter thinks ORT is multiversal)
It is also technically described as an extremely vulnerable state where Arc could die from her emotions running amok and her soul (without a body as a container) essentially evaporating in a citybusting (yes, it's directly referred to as a city-destorying calamity) explosion. However, it is speculated the Lumina form could be used to birth a stronger individual-though this would be tantamount to ego death to the original Arc. Kind of like if you shot Tamamo and she regenerating Doctor Who-style into Koyan to be better at taking revenge.
Her next major buff she gets is the Event Storage ability common to all True Ancestors. Basically she creates a black hole and crushes all matter, energy and information nearby-with the potential to literally rip off an entire Texture of reality and store it somewhere. Yes, this does look very similar to U-Olga's black hole powers.
Finally, she gets something called Mana Burst (Star) in TsukiRe which is also referred to as the Skill Breath of the Planet in her Archetype Earth Servant form in FGO. This one is the least convoluted: Simply by breathing, she inhales existing magical energy and converts it into a net increase of energy, described as a "Mana Cleaner". Curiously Archetype Earth's Mystic Eyes are implied to be stronger than regular Arc's even in her Servant form, inflicting true paralysis instead of just charm-implied to have something to do with fully embracing her status as an Ultimate One rather than suffering the various nerfs of Tsukihime-timeline Arcuied. Also instead of just being a misunderstanding-induced nerf, Archetype Earth has somehow turned Funny Vamp into a teamwide slew of vague buffs that protect the virtuous (enough to grand Invincible to allies, and refill some of their mana if the Marble Phantasm is deployed. Or automatically, if they are living humans)
...also Phantasmoon shows that due to some combination of the above, Arc has the ability to modify herself in real time with a combination of stealing a magical artifact (Medea's staff) and getting a new hyperfixation. In this case, Christmas. While this was actually mostly a flat nerf on most fronts because Arc is retarded, the Phantasmoon statblock DID show that Arc can teleport through the planet's leylines, alter the status of being an Ultimate One into becoming "the incarnation of Christmas", turn Breath of the Planet into a team-wide buff somehow, have her Mystic Eyes punish the naughty and reward the nice instead, and conversely turn existing team-wide buffs into selfish buffs. Also while it is objectively more shit, Phantasmoon's new NP shows that if she wanted to Arcuied could create a nerfed subtype Marble Phantasm that does SPECIFIC complex things like turn her into a superpowered magical girl/astronaut/Santa.
TLDR FGO and TsukiRe really want to stress that ultimately, despite giving some justifications, limits and elaborations Arcuied's powers are ultimately greatly influenced by what Arcuied herself wants. She's like a Chaos God but bad shit happens if she tries to expand her influence beyond a person-shaped container because her soul is too volatile and apparently the Earth's magical energy is fucking intense.