Rule Breaker: All Spells Must Be Broken (also known as the Destroyer of All Talismans) is Caster's Noble Phantasm, a weapon that materializes the divinity of the witch of betrayal herself. It is an iridescent and jagged dagger that is thin, brittle, and blunt. It has the combat efficiency of a regular dagger, and it would not be suitable for killing a single person. Its true, actual purpose is that of a key used for rituals that is described by Caster as an "indulgence from the Age of Gods that is forgiven by anything for one purpose." Shirou Emiya feels an ominous feeling every time he sees it, realizing it is dangerous to servants after inadverdently analyzing it, as it manifests as a feeling of pain in the Command Spells on his hand.
Its unique ability is that it is the ultimate anti-magic Noble Phantasm capable of dispelling and destroying any kind of thaumaturgy. Upon coming in contact with the ensorcelled item or person, enchantments, connections bounded through contracts, and creatures created and maintained by prana will all be returned to their original components in a state "before they were made." It is a blade of betrayal that will sever all connections between a Master and a Servant by, as its name implies, breaking and therefore destroying every single rule that controls them, giving full control of the Master's Command Spells to Caster. She uses this on Saber and Archer, causing Shirou and Rin Tohsaka's Command Spells to disappear and transfer to Caster after their contracts are nullified. The Servants themselves must be the target, as it actually has no effect on Shirou's contract with Saber after simply stabbing his flesh. It is also capable of severing Angra Mainyu's hold on Sakura Matou that had turned her into Dark Sakura earlier after it is projected by Shirou. There is a limit to what Rule Breaker is able to dispel, meaning artifacts on the rank of Noble Phantasm will never be returned to their original state no matter how low their rank.