A unit with spirit sight suffers no penalty from darkness, and has no penalty when attacking invisible or unseen units. A commander with this ability will also negate the effects glamour has on the strategic map, but only in their current province. This effect will however only reveal units that are not currently carrying out stealthy orders.
Only units with this ability are counted when attempting to find invisible units when patrolling. Unseen units do not require spirit sight to be caught.