Vengeance for Prospero

Use this Stratagem just before a Thousand
Sons unit from your army fights in the Fight phase. Until the end of the phase, that unit's Death to the False Emperor ability triggers
on a hit roll of 4+ instead of 6+ for attacks
that target a Space Wolves unit.
The Thousand Sons have never forgiven the
sons of Leman Russ for the destruction of their
home world.