Decay

The Decay Layer is similar to the Delay Layer, as it influences the temporal course of changes (due to fields/modifier layers arranged before it in the field list; which also includes color changes, for example) and can therefore also have an effect outside a field influence area.

If, for example, a clone moves from one animation frame from Y = 0 to the next to Y = 100 and then to Y = 0 again, i.e. performs a sudden movement, the Decay field ensures that this lightning-like movement is transformed into a slow decaying movement (the speed can be adjusted).

To describe it a little more precisely (and to distinguish it from the Delay Layer): it is a lightning-like increase in value with a delayed decay (or vice versa).