The Hero may want to save before they use this, so that if they miss with the ability, they won't have to wait for the 1 in-game day cool down time.
When casting Warden Key at a gate, the wall close to the lock should be targeted.
Note that the Warden Key greater power granted by the doomstone acts as a more powerful "open lock" spell than the spell one receive if one choose the Tower as the original birthsign. When using the spell, remember to aim extremely carefully at the lock, or door which one wish to open. It is easy to miss when casting at the target, and if one do miss the only option will be to try to pick the lock, use another spell, or if one do not have access to either possibilities, wait 24 hours for it to recharge. This can be very inconvenient.