Troja

Commercially-published variant of Chess. The major change is that pieces, apart from the king, can be attached to other pieces of the same player. The highest piece is called the Trojan figure and it is the one whose movement mode controls the movement of the conglomerate. Once attached, pieces may later be detached. As you might expect, there are also some special rules around pawn promotion, e.g. only queen per side is permitted.