Multi-Dimension Bomb

A Multi-Dimension Bomb (マレチディメンションボム), also known as an MD Bomb (MD爆弾 MD Bakudan) or MDB, is a weapon that Kokonoe tricked Ragna the Bloodedge into thinking that she had implanted it within him. Whether Kokonoe actually owns this weapon or if it even really exists is unknown.

Information
During the events of BlazBlue: Chrono Phantasma, Kokonoe tricked Ragna into thinking that she had put this device into Ragna's left arm, having him believe that she had done so after having fashioned him a new arm created by Lambda-11's regeneration tank at the end of the Continuum Shift. She told the Grim Reaper that should he ever stray too far from Celica A. Mercury, then the bomb would detonate. In reality, the MDB was actually a Noise Canceller created by Kokonoe, and the lie was fabricated to make Ragna and Celica spend time together, allowing the Noise Canceller to tune itself to Celica's wavelength.

According to Kokonoe, the bomb itself could be attached to someone's cellular level, making it impossible to remove. Instead of exploding, it would implode, only effecting the body it was attached to and making civilian casualties impossible. Kokonoe also told Ragna that she could activate the switch at any time if she wanted to, allowing her to control the Grim Reaper.

BlazBlue: Central Fiction Library Entry
''Something Kokonoe lied about implanting in Ragna's left arm. In reality, she didn't implant an MD Bomb, but instead installed a 'Noise Canceller' in order to gather data. Kokonoe simply lied about the MD Bomb to keep Ragna constantly near Celica and under her influence. It can also be called an MDB.''
 * MD Bomb