Champions of Rokugan Coop Variant Play Through with House Rules - Oni Summoning

About Champions of Rokugan, from BoardGameGeek:

Champions of Rokugan is a cooperative board game with miniatures for 1 to 5 players set in the fabulous world of the Legend of the Five Rings. These Rings, representing the 5 elements of this universe (Fire, Air, Void, Water and Earth) will serve your characters both in their actions and to trigger special abilities. Each player will embody a Champion of the major Clans (or a Ronin) of the Emerald Empire, vying for the Emperor's favor. Samurai, Master of the Elements, Courtier or Ninja, their talents will be put to the test in these tormented times, where danger lurks everywhere: from corrupt beings coming from the Outworld to the enemy within and the many factions ready to overthrow the Empire. The Empire's path to Honor and Glory is demanding, and there are many dilemmas and pitfalls to keep you from it. Succeed in honorably facing the dangers that stand in your way, or fail collectively. But ... remember that saving the empire doesn't exempt you from your duties to your clan, and that one man's glory is another man's disgrace... -description from the publisher