oooh fun choices! blazes are a bit hard, mainly because iâm on the fence about whether i prefer them as natural creatures or artificial creations of whoever built the nether fortresses. either way, iâd define them as a magical entity, which to me are in an entirely different taxonomical domain to regular cell-based life. if they are naturally occurring, i like to throw around the idea that theyâre extinct in the wild but were bred in captivity [whether the blazes we know are the same ones that existed in the wider nether or a domesticated form is a whole other point of consideration] and have just kinda spilled out into the nether fortresses now that whoever built them is gone
while that might not have been quite what you were hoping for, i do have some properly speculative biology related ideas about ghasts!
most of a ghastâs body is empty space! theyâre basically just a big flight membrane stretched over a cartilage skeleton, like so:
there are several benefits to this hollow structure. first, it helps them to stay cool in the intense heat of the nether, as air can blow through and ventilate its body. secondly, itâs how they fly! they catch wind in their bodies and, because theyâre so light for their size, this slows their descent to a crawl and lets them steer themselves around like a kite, catching updrafts as they go and precisely manipulating the air in their bodies to stay airborne effectively forever. the tradeoff is that theyâre so specialised for gliding that they canât afford to stop - a grounded ghast is as good as dead, as they have no means of getting back in the air by themselves.
as a side note, the netherâs extreme temperatures and cavelike structure make its atmospheric conditions pretty wild, so a ghast in the overworld or end will have significantly more trouble keeping itself off the ground. in general most nether mobs donât take well to the pressure and temperature changes in other dimensions, and vice versa, hence why thereâs very little overlap in each ecosystem despite an apparent history of portals being used
and unrelated, but ghasts âcryingâ is actually how they keep cool! that minimalist body structure doesnât leave much room for internal thermoregulation, so the aforementioned air ventilation and constant stream of tears have to pick up the slack. [if weâre being pedantic itâs technically sweating rather than crying, but nobody wants to drink a potion with 'ghast sweatâ in it.] what little moisture is in the air they pick up is collected by some weird organ or other and recycled constantly into tears. since water is so scarce in the nether iâm guessing its native species evolved not to need it at all, so flushing all the moisture they collect right back out is no problem for the ghast.