How to close final fight portals?

[Thelo]

In the final fight against the sorcerors, how do I actually close the invocation portals that spawn enemies? I tried walking onto them, pressing the < key while stepping on them, and attacking them, but the portals continued to spawn enemies. I accidentally ended up getting the achievement for beating the sorcerors without closing the portals that way - but all I wanted was to close them!

What did I miss?

[bendenny]

Use the corresponding orbs of whatever.