To remove the spell activate the pillars with blue and yellow halfs of full moon.
In the second part of the puzzle you have to activate the pillars in the order of moon growing from crescent to half to full and back to half and to crescent. If you morph, you'll see an activateable rock with a clue in the room. Also, there is a circle on the wall with all phases of moon shown.
When you activate the correct one, it'll disappear from the circle. If the time runs out, just activate the Full Moonstone again and continue from the point you've stopped at.