Custom pieces
Ten custom pieces are built-in: King's Hand, Archer, Dragon, Barricade, Portal (swap with a friendly piece), Necromancer (resurrect a captured ally), Shapeshifter Pawn (transforms into whatever it captures), Juggernaut (a 2-square siege engine — auto-pairs on placement; charges, tramples, immune from the front), Assassin (slides up to 3 diagonal squares then 1 step in any direction), and Wizard (rook moves that hop across opposite-colored squares — bound to its starting color).