Castle of stone

A glowing green glyph with curves and edges crossing it covers the area. and the earth cracks and shakes as magic cuts the earth raising up a great stone tower from the earth. the size of the area able to be transformed is doubled for every caster that helps in the ritual, up to a maximum of 5 casters. 

able to create a tower of stone raised up from the ground 30 foot wide and 50 feet tall. underneath the tower is a large stone pillar that holds it from falling back into the hole created from its formation.