????????
      +---------
JWQQG | TQPLPJNW
       -JWQQG
        =====
        LTWJRJ
       -LJHPNH
        ======
          QRTWN
         -GNHHL
          =====
          LTWMFW
         -LJHPNH
          ======
          ??????

base: 13
letters: EFGHJLMNPQRTW
difficulty: challenging
missing: E