I recently bought one second hand and the guy included a power supply that wasnt eventide branded and is also rated at 15v.
Does the pedal run at 15v (i'm presuming its not designed to as it says 9-12v next to the PSU input) and would it do the pedal damage if its been using a 15v power supply till now?
It may well damage it, and certainly will not be covered by warranty.
Please use the power supply it was designed for.