Stamp an enemy knight or bishop. In 6 of your turns, if it still lives, the librarian drags it back to an empty home square of its type on the enemy back rank (or any free back-rank square).
You draft Overdue Library Book in Buff mode. Free action: you choose when to use it, and it resolves without costing your turn.
As a attack card, it removes or detonates a piece directly.
“The fines are measured in tempo.”