Let's talk Illians.
Been playing nothing but them all day.
First of all, is that the build speed of workers on Ice is extremely slow. This causes some annoying management of cities, because you generally want to build improveents first before the temple, and you aren't going to fully build up a city very quickly before you want that temple in most cases, and so you end up taking longer than normal.
Second of all, I'd like to see Ice mana get a bit more use. As it is now, it's almost completely irrelevant. You are almost the only civ that can get it, so the things you can do with it are only about on par with the Malakim summoning Desert lions.
Also, as far as I can tell, you can't build more nodes for it, and even if you could the second source doesn't seem to give promotions the way it ought to.
here's my thoughts on what to change here:
1) Give the illians a unique Adept with the ability to build Ice nodes with Elementalism.
2) Ice mana gives +5% Ritual Production (per source)