[persnickety]

The rat scroll removes points from the board (replaces monsters with 1hp rats).

[prawn]

The rat scroll reveals rats.

As you find rats, they are facing towards the rat king, which helps you locate it, get the scroll, and reveal cheap kills.

[tomgp]

Does it? I thought it just revealed the rats

[persnickety]

Huh, now I have to check.