Homebrew
Abjuration cantrip
Casting Time: 1 reaction (which you take in response to you or an ally within 30 feet of you failing a Saving Throw)
Range: 30 feet
Components: V, S, M (a miniature cloak)
Duration: Instantaneous
You channel magical protection to the creature who failed the Saving Throw. That creature can roll a d4 and add the number rolled to the save, potentially turning it into a success.