Spirit

If you have the following: Units that can use this synergy:
 * 2 Units: When they attack, Spirit units have 25% chance to silence their enemy for 3 seconds.
 * 4 Units: When they attack, Spirit units have 35% chance to silence their enemy for 3 seconds.
 * Ghost.
 * Troglodyte.
 * Dryad.
 * Moon Doe.