The arcane lock spell says that a closed door, window, gate, chest, or other entryway "becomes locked". The spell says
it is impassable until it is broken or the spell is dispelled
Okay, impassable is pretty clear, but it's last part of the spell description that confuses me:
the DC to break it or pick any locks on [the object] increases by 10.
Again, the break part is clear: the locked object is off limits unless you can break it with an increased DC. But where does pick any locks fit in? Is the implication that if the door or chest is locked, picking that lock at the increased DC will defeat arcane lock? What if the chest wasn't previously locked? And, if this applies when the chest has a lock but not otherwise, what about the addition of a lock makes it possibly easier to defeat than otherwise? If the object wasn't previously locked, can it now be picked with a DC of 10 (increased from the previous DC of 0)?
Or, is it that one can pick any locks at an increased DC, but the object is still impassable? If so, what is the point of raising the DC? A kind of wizards' ha ha to the rogues out there?