Dark Matter is a cupped hand with some form of dark (Possibly demonic) aura around it. When picked up, Isaac's eyes disappear and are replaced with empty eye sockets with small, dark rings around them. Isaac's tears also turn black with a trail of darkness behind them.
Isaac's tears now have a 50% chance to inflict the status effect Fear. This will cause most enemies to part from their original path to avoid Isaac. This can be used most effectively as low Health characters such as Judas, ???, or the Lost.
Monstro's Lung - Fear effect stacks. All projectiles fired will be affected by Dark Matter, greatly increasing the chance of fear being inflicted.