Η is vowel in ionic and modern greek.
But it's velar or even guttural in other dialects:

H turns into vowels in japanese and somewhere else (I didn't remembere where, so I started this file to put it here afterwards)

Н is N in russian. and И is I which relates it back onto Η, which is natural, because И is officially a form of Η calqued onto russian looking just like Η and their Н was N, but then for whatever reason they rotated those dashes counter-clockwise, and boy it didn't make us happier, being more different from latin than we even were. divide et empera as sociophaths say, fucking cure those fucks already!