Prismatic Palisade

If successfully cast, set up a Prismatic Palisade
model wholly within 18" of the caster.
At the start of each turn, roll a dice for each
unit within 6" of this model. On a 5+ subtract
1 from hit rolls for that unit until the end of
that turn.
Blocks line of sight if a line between the centre
of the attacking and defending models base
crosses any part of this model.