I have Terrakion, Virizion, Cobalion, and Keldeo. I'm at the boulder with the three markings in the pledge Grove, but Keldeo won't react to it.
Your Keldeo isn't an Event Keldeo, so it was most likely a hacked Keldeo. Only event Keldeo will react to the Pledge Grove.
How to change your username
How to add a user avatar
Why was my post hidden?
Flags vs Downvotes
Official PokemonDb League
Type a Pokemon name, type, move or ability to see instant results.