Doom Siren

Uses a special Doom Siren template, which is positioned as desired and then moved straight forward for 21”. The Doom Siren‘s Strength begins at 7, but loses 1 point for every 3” of distance. If it hits a vehicle or building it will inflict a hit on a random location and then stop moving. It will move over hills and low walls.
The save modifier is equal to half its Strength value when it hits, rounded down.