Legion's Hold Trap (4e Trap)
From D&D Wiki
A magical object taking up one square, such as a stone pillar with a Black Orb on the top, which causes it's victims to stop in their tracks. Once the pillar is destroyed the Orb will fall and crack, harmlessly shattering into pieces of glass.
Players can make a DC 30 Arcana knowledge check to identify it when they see it.
This trap can be used to make adventurers vulnerable to attacks from other traps or from monsters. It can be used to great effect in fights with monsters immune to psychic attacks, as the burst will not affect them.