Remember in The Ring when Samara kind of walks backwards but still towards you and it's all scary and weird? This is not really like that.
However, Reverser does delay and reverse sections of the input sound resulting in anything from hauntingly eerie textures to reverse percussion hits:
Reverser shines on it's own, but it was primarily created to power up the different "Snapin Hosts" Kilohearts offer. These are bigger effects units that utilize all the available snapins and give you a really fun and creative workflow for combining them in any way you can think of. So have a look at Snap Heap and Multipass right now.
Reverser is also available as a Rack Extension for Reason over at the Propellerhead shop.