The Caro-Kann Smothered Mate
The e7 pawn is pinned by the queen, so Nd6 is mate: the king is boxed in by its own pieces.
Opening: Caro-Kann Defence. Set by White. Level: Intermediate.
Practise setting and escaping itThe moves
1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nd7 5.Qe2 Ngf6 6.Nd6#
It only works after a mistake
Black must play Ngf6 for it to work. Qe2 is a normal move here, and the trap costs White nothing.
How to avoid it
Ndf6 or e6.