Firescales (and by extension flame-less dragons) can have bright/pale green eyes or any color that isn't regularly found as a skywing eye color. Samething for skywing animus dragons as sead above for firescales.

Flame-less dragons are 100% fire proof.

During Darkstalker's time it wasn't abnormal for nightwing wings to looked more bird-like or for them to have more owl like patterning. But due to life on the volcano not needing these traits they diapered over time.

Animus magic was likely magically gifted to the sandwings, at some point and that's why it isn't more wide spread and why it died out with Jerboa.

The spell that broke animus magic would not- and does not affect Darkstalker's scroll.

Twin dragon eggs are rare for every tribe but more common is skywing society.

Twin dragons from any tribe have their own versions of a firescales and flame-less dragon

for mudwing twins it'd be a heavy scaled dragon (Scales are thicker and harder to penetrate- also making them slightly fire resistant) and a "Scaleless dragon" (Softer scales overall.) For seawing twins it'd be a glow scales (All scales are bioluminescent) and a lightless dragon (no bioluinesenct scales)

for Sandwing twins it'd would be heat scales (like flame scales but less intense as they just give off more heat, can give a dragon a mild burn) and plain scales (no extra heat comes from their scales) For rainwings it'd be venom scales (Like firescales but with rainwing venom contently oozing from their scales), and venom less.

For nightwings it'd be black out scales (All scales are black with no hints of other colors or silver scales, unless they're a mind reader) and moon shine scales (Completely silver dragon with no black, but the silver tear drop would be black if they were a mind reader.) for Icewing twins it'd be frost scales (Like firescales but with ice instread) and ice less dragons (The would also not radiate any kind of cold.)

for hivewing twins and silkwing twins I don't really know as their powers are kinda all over the place, I think they'd its more likely that they'd be conjoined twins. And for leafwing twins one would have leaf speak and one wouldn't even if both parents don't have leaf speak. This is how leaf speak wouldn't die out like the icewing's animus blood line.

All leafwings have a connection with plants, for some it's strong enough that it manifests into leaf speak.

okay that's all of the ones I can think of as of right now- but if you got any I wanna know! Also feel free to use any of these head cannons in aus if you want. Personally I think that the twin head cannons are my favorite ones I have for the series.