How do you use astral gems?

[alexti]

How do you use astral gems when they're in abundance?

For example, for nature, earth gems and water, there's plenty good summons. Death gems are good for both summons and Skull Mentors.

There're many good items requiring astral gems, but later in the game astral gem income is often larger then the forging costs (unless one starts making magic items for nearly every commander).
Sometimes I use them for the protective dome.