The observer calls in indirect fire: for your next 2 turns, your rooks may capture an enemy piece along a rank or file even when exactly one piece stands in the way. The blocker is unharmed; the rook lands on its target.
You draft Forward Observer in Buff mode. Passive: it works on its own the whole time you hold it, with nothing to activate.
As a attack card, it removes or detonates a piece directly.
“Eyes on the far ridge, shells over the hill.”