Looking for a story

I'm looking for a story.
It starts out where a boy and his friends are role playing a story from their mmorpg. They are out back of his grandmothers house where there is a teleport circle. As they continue the game they use an ear ring they found in her library. A being underneath the circle notices them and decides that they need changes as they are not the right sex to hold the power it decides they need.

Update I remember that the witches (grandmother's) group were there to seal demons.

I'd appreciate any help.
Rachel Anne