Copyright (c) 2001 Peter Aronson

MOVE - Both the Towers and Castellans moves like the chess Rook (i.e., any number of empty cells in a straight orthogonal line), and may leap orthogonally over an adjacent piece, landing on the next empty cell. 
Castellans may additionally step a single cell diagonally, but not to the red cell, and without capturing.
A player's pieces may not enter their own red corner cell. 
Moving as so as to repeat the previous position is forbidden.
CAPTURE - There are two ways of capture:
Custodian - If a piece moves orthogonally next to an enemy piece and there is another friendly piece directly beyond that, the enemy is squeezed between the two pieces and captured.
Intervention - If a piece steps between two orthogonally placed enemy pieces, it captures them both.
It is possible to move so as to capture in more than one direction at a time.
Pieces on corners may be captured by occupying both orthogonally adjacent cells. Red cells act like enemy pieces for both sides for purpose of capturing.
Capture is mandatory, except if the player's Castellan is threatened or can move to the opposing red cell. However, if the only capturing move is with that Castellan, the player must still make it. 
The player may choose among any available capturing moves.
GOAL - Wins who captures the opposing Castellan; or moves his Castellan to the opponent's red cell; or stalemates the opponent.

The author says: This game was synthesized from a number of sources: description of the obscure Thai and Malay games of Mak-yek and Apit-sodok from Murray's A HISTORY OF BOARD GAMES OTHER THAN CHESS, Vuthy Tan's description of the game of Rek from his article "Cambodian Chess Games", the Japanese game of Hasami Shogi, the old Viking game of Hnefatafl, and a little bit of Checkers. [...] The game often revolves around long series of forced captures. It is often necessary to consider where a sequence will end up before starting one. Careless play results in very short games.

An example

Green Castellan moves to h6 and captures Tower h7. Black cannot stop the next winning move h6-h8.

There is a ZRF to play Towers with Zillions.