A single Screaming Bell can be deployed in each unit of Clanrats or Stormvermin. Place the Screaming Bell at the front of its unit, as centrally as possible. The following rules apply.

Moving the Screaming Bell

The unit the Screaming Bell has joined marches, charges, and pursues normally so long as it has at least 10 models. For every model the unit drops below 10, the unit deducts 1" from its move. If the unit is reduced to five models or less, it cannot move.

Terrain

The Screaming Bell treats terrain in the same manner as a Chariot.

Shooting at the Screaming Bell

Any enemy can choose to target either the unit pushing the Screaming Bell or the Screaming Bell itself. Hits against the unit are resolved as normal, but hits against the Screaming Bell are randomised - hitting the Screaming Bell on a 1-5, and the Grey Seer on a 6.

The Screaming Bell in Combat

The Rat Ogre crew and Grey Seer may fight anyone in base contact with the Bell. The Rat Ogre can fight in close combat and still ring the Screaming Bell. Enemy models in base contact can choose to attack the Screaming Bell or any character mounted on it. Attacks against the Screaming Bell must roll To Hit against the Rat Ogre crew's Weapon Skill.
Count the Screaming Bell as the same number of Skaven that would normally occupy that space (usually 15) for working out the rank bonus of the unit.

Destroying the Bell

If the Screaming Bell itself is destroyed, remove the model and place the Grey Seer where it was. He will join the unit. This is the only way the Grey Seer can leave the Screaming Bell.