Black Coffin Capture Ritual

This powerful containment ritual conjures a giant black coffin that contains anything within its radius. The coffin is extremely difficult to destroy and is full of pure darkness that cannot be seen through by any means

Procedure

 * 1) Draw a square of black chalk
 * 2) Within 1km of the black chalk, clap your hands and chant "Close, coffin, so mote it be"