[Red Badger]

There’s more than one monolith. They are guardians of primitive but sentient life forms................

[Carry_Okie]

There’s more than one monolith. They are guardians of primitive but sentient life forms................

The book had one on the moon, one on Japetus, and I recall dimly that there was yet a third on another world to which Dave Bowman had been transported. They were a portal of sorts bypassing limits of linear space-time.