"Center of the floor is fine. Let's start with the obvious, see if I can directly cancel an effect on you. It won't work, wouldn't even work on a regular anti-economagical field, but let's try anyways."
Albe extends a hand toward the murky walls of darkness, takes the arm-length cylinder of polished metal that smoothly extrudes from it that dark wall, and then gestures at Merrin with her other hand, the one not holding the metal.
"Nope," says Albe. The metal cylinder floats back into the wall, replaced soon after by a thin cylinder of polished wood. "All right, let's try the elemental energies in order. This one is what we'd term Positive Energy. Try poking it with the tip of your little finger first, it's not dangerous but good practice for when we try the more dangerous ones."
There's a sphere of blazing pure white light within easy finger-poking reach of Merrin.