Holy trinity

Use this Stratagem in your Shooting phase, when
an ADEPTA SORORITAS unit from your army
is selected to shoot. Select one eligible target for
that unit that is within range of, and visible to, at
least one model in that unit equipped with a bolt
weapon, one with a flame weapon and one with
a melta weapon. Until the end of the phase,
models in that unit can only make attacks that
target that enemy unit, but each time an attack
is made with a bolt weapon, a flame weapon
or a melta weapon, add 1