×It seems the only way to strike the seeding beacon is by reentering its chamber with your sword from the west. But stepping on 1 traps you in there since you need evil eyes to hold the doors open.
While I can see maybe using 1 mirror to hold down a plate, you need another mirror on the lower right plate and there are no other usable mirrors.

×Need to use an aumtlich and a mirror to hold open the doors the second time through.