Sylverant is a homebrew open source server for Phantasy Star Online. Dreamcast users still play PSO online with this server even today! This is the official forum for both the online game server as well as the open source project itself. Feel free to post and get a gathering started online! We can also show you how to get connected!
I never played through the offline mode. Was just too damn boring
You never had to do anything with the monoliths in online mode (other than walk up to the one where dark falz is hibernating). So, What is the function of the monoliths in offline mode?
When you beat Vol Opt offline, a green warp appears instead of the red teleporter. The warp takes you to the entrance of Ruins 1, which is blocked by a seal. You must activate all three pillars to remove the seal and enter Ruins 1. The pillars don't work until after you beat Vol Opt for the first time, which means you must play the areas twice to unlock Ruins. Sega lifted this requirement in GC by allowing you to activate the pillars the first time you play each area.