There are many paths forward from that point. The spacetime rift has most of them, and the old man there explains what to do then.

You don't have to do any particular ones of them. But you can:-). Especially with the powered up pendant that you got from the Mammon Machine (necessary to even get to the area where the queen is), you can now go back and open up all the doors and treasure chests scattered throughout the game that were locked with "a mysterious power". Hopefully you wrote them all down in your notes taken while you went through the game!? Or just consult a guide, even if only for that one thing. Plus I thought the game showed hints to remind you.

There's SO MUCH to the game past that part - you are missing the absolute best of it!:-) But yeah, seriously, use a guide for that part - no reason that each person has to do all the discovery entirely on their own. Or just muddle through the boss fight using items - that will take awhile and be frustrating as you get confusion put onto you (hint: there are multiple types of helmets that protect against that...), but it does work, as that is how I beat it the first time myself without a guide.

Do as you please, but it's a fun project to see what's beyond that point in the game!:-)

In part bc damn is that music great to listen to!!:-)