How do you use astral gems?

[Pocus]

cestkoi ROE?

I can understand why Alexti asked the question on first instance though. Thats because astral does not have low level summons, so one can be under the impression that there is a lull, in astral gem usage, compared to other paths.
But I dont think that somebody can seriously say he has too much gems in his labs, or it means you have won against the AI, but dont want to end the game to toy with them a bit more.