If the target succeeds at the saving throw, it can't be used against that target for 24 hours. Also, a creature that can see invisible objects notices the sensor. If targeting an area instead, the sensor doesn't move so that is also a limitation.
So, some limits, but still quite powerful as befits a very rare or legendary item.
I basically was asking if you could cast this all day long - yes the save DC is a limit, but you could spend 12 hours scrying a large area....
You could, but what would be the point of that? Seems like a boring way to spend playing the game. That's a situation when I as a DM might hand wave the plot forward, or provide the other players an opportunity to do their own downtime activities. Or maybe even use Sending Stones to allow the one using the Crystal Ball to be the "eye in the sky" to warn players about threats or have books ready to provide Intel.
You could, but what would be the point of that? Seems like a boring way to spend playing the game. That's a situation when I as a DM might hand wave the plot forward, or provide the other players an opportunity to do their own downtime activities. Or maybe even use Sending Stones to allow the one using the Crystal Ball to be the "eye in the sky" to warn players about threats or have books ready to provide Intel.
That sounds cool. Batman and Robin out in the field, Oracle or Alfred scrying in.