Burn it down!

At the end of each of your turns select a piece of
terrain that you control to set alight. Until the
end of the game whenever a unit starts or finishes
any type of move within1 inch of that terrain,
they take d3 mortal wounds. Complete this
mission at the end of the game if you have set
alight 5 different pieces of terrain.
Boon:—
You gain a triumph of your choice for all future
battles.