Skulk Sensors

Whenever a player casts their second spell
in a turn, untap target artifact.
The mechanisms of the skulk-filled ancient cities
are run not by gears and turbines, but whispers
and cries. Mechanisms, which for millennia
have sat quiet, roar to life upon the footsteps of a trespasser. They require no coal. No redstone.
The echo of life is far more potent than both.