The First Edition describes the Taint as follows
[The Shadow Taint] Obsession constantly urges the Solipsist to create chaos and disorder, to demolish structure and abandon narrative. Once a Solipsist has this Obsession it will apply to their Changes whether they want it to or not, if their intended Change has any of these elements. This may cause the Solipsist to make uncontrolled Changes and eventually result in them gaining Tears.
This is all true, but it doesn't go far enough to represent the way the Taint has caused chaos in actual play. I plan for the second edition to say the following
The Shadow Taint is recorded as an Obsession, but it will act as both an Obsession and a Limitation in play depending on what furthers the Shadow's aims most effectively at the time. It acts as a Limitation (raising the difficulty) whenever the Solipsist wishes to defeat the Shadow, resist an Un-Change or resolve a Thread. Conversely it acts as an Obsession whenever a change would further the Shadow's aims, causing chaos and disorder, demolishing structure and abandoning narrative. Where possible the Trait will also cause the Solipsist to Overshoot. The Trait will not cause overshoots when the Shadow is not active, though it will lead the Solipsist to create chaos.