Sneak and every player within a 6 block radius is pulled 3 blocks toward you. The Kappa deals nothing.
Its value lies elsewhere: cancelling a disengage, dragging back a target running for their refill, gathering two opponents in the same place. It is the only kit on the server that decides other people's position without touching them.
The well does not choose. Pulling to catch a runner also brings back the three players you had not seen. In a 1v1 it is a tool, in a general melee it is a risk — and it is the same key.
The cooldown starts even if the well catches nobody: otherwise it would be a free presence detector, usable on loop.