On Revlid's Elementals: Are they purely a phenomena of Creation, or can they happen anywhere there is a pole of elemental essence?
Does Autocthon spawn Oil elementals? Malfean Vitriol ones?
Or is it a mechanism like the loom, where Autocthonia and Malfeas have their own differing methods of resolving essence imbalances?
Not Revlid here, but I'll make a guess-statement.
Autocthonia has elemental poles, and they probably have similar mechanisms to Creation's one, because Autochthon is a sick cripple who can't self-regulate his body processes and he needs elementals to stop himself from
shitting the bed and dying smoking the bed and dying.
Healthy Primordials, on the other hand, naturally self-regulate their essence flows. Sure, occasionally waves of Kimberyian essence will create horrifically poisonous toxins which melt even the things which naturally live in her, but that's just part of being Kimbery. If you get
strange things in Malfeas, it'll be odd short-lived things which appear at the boundaries between the Yozis, where their Mythoi are forced up against each other and grate and rub and their essences clash. They're not exactly elementals, but they're more akin to elementals than demons.
They also have a lifespan even shorter than your average First Circle in Malfeas, and usually blow up, tear themselves apart, or are squished by the Yozis immune systems pretty quickly. They're mostly of interest only to scholars, and sorcerers who've developed spells to pluck one from Malfeas and fire it at their enemies to explode.
On a Creation note, besides elemental summoning, does this mean you have a choice between building a manse with care for established geomancy, or building a manse faster then having to defend it from Angels elementals trying to fix it?
Well, that certainly sounds fun and gameable and makes "let's make a new demesne!" into less of a no-brainer - it makes taking and holding land just so you can get access to its
oil demesnes.
So I'd totally be in favour of that.