Over the next few sessions, my group are likely to find themselves in the Astral Plane in pursuit of the current BB. They will be level 4 when this happens.

However, I'd like being in the Astral Sea/Plane to cover at least a whole session in terms of combat, exploration etc, before meeting the boss right at the end when they find his mansion on an island.

I've read what the DMG says about the Astral Plane and the only real information it gives is that the Gith live there; currently the party are too low level to really be fighting Gith forces (I know I could adjust the stat blocks, but I'd rather leave the Gith alone for now). 

Are there any other known monsters/civilisations/living things in the plane that the party could encounter, fight, get to know, etc?