The Restraints of the Round Table (円卓拘束, Entaku Kōsoku?) are thirteen restraints set upon King Arthur's weapons by the Knights of the Round Table, applying to both Arthur Pendragon and Artoria Pendragon. Excalibur Proto for Arthur and Rhongomyniad for Artoria possess the restraints. It is unknown if Artoria's Excalibur possesses them, but it does bear similar conditions to activate its most powerful state.
For Excalibur Proto and Rhongomyniad, over half of the restraints must be released in order to release their True Names. For Excalibur, each condition passed allows for more power to be utilized. It is unknown if every single condition is shared between all the weapons or if they vary depending on the world.
- Bedivere: The enemy must be more powerful than oneself
- Palamedes: The battle must be one-on-one
- Lancelot: The enemy must not be an elemental
- Mordred: The battle must be one against evil
- Galahad: The battle must not involve personal gain
- Arthur Pendragon: The battle must save the world.
- Unknown: The battle must be an honorable one
Fate/Prototype Tribute Phantasm
"Proto Saber's Excalibur is locked by two seals, one being Barrier of the Wind King, the other being 'Restraints of the Round Table'. Some examples of the Restraints including:
-The battle must be an honourable one
-The enemy must be more powerful than yourself
The seal will be released if more than half of the thirteen Restraints are passed."