There are three rule sets I came up with for playing with these cards.

Standard

• Chieftan and Boss cards are treated like all other cards when building your deck
• Really doesn't count as a distinct rule set.

Commander

• 2 Chieftan cards and 1 boss card are required for each player, but you can't have a greater number of either in your deck
• Chieftan and boss card costs are all halved(rounded up).

Raid

• Raid is a very different way to play the game
• Choose one player to be the raid boss, the other player is the raider
• Raid boss player chooses a boss card, a chieftan card, and a card pack.
• Raid boss player opens 9 of the chosen pack, and places each card obtained in the deck(unstacked) alongside 1 copy of their chieftan
• The raider constructs a deck as normal (intended rules: no bosses or chieftans, max point value 128, maximum of 28 cards).
• Raider goes first. 
• Whenever a raid bosses card is killed, it is set aside, on the raider's turn, they can choose to use an action(aka an attack opportunity) to place one of these cards in their deck, they can only do this once each turn, they can't choose a Chieftan.
• when the raid boss would draw, if they have no cards in their deck, they place their boss card in their hand. They can only do this once.
• when the raid boss's boss card is killed, they lose.

Chieftans

• Chiromaw Matriarch: Attack 12, Health 6, Aspects; Yunugaz (Wind), Ordaniis (Enhance), When defending a card with Stomach, this card isn't destroyed, but the defense immediately ends. Crafted with a Beloved Friends pack and a chirobarb erupter.
• Barishee:Attack 11, Health 8, Aspects; Freiwynn (Vision), Dayuniis (Mind), This card can attack and defend exactly 1 card each as part of the same action. Crafted with a Sludgeon Delver pack and a rune door key.

Bosses

• Dreadful Peat Mummy: Attack 12, Health 8, Aspects; Armaniis (Desire), Byrginaz (Water), Celawynn (Stomach), After Stomach activates, this card is permanently considered defended. (Leaving the defended token is a good way to indicate this.) Crafted with a Disturbed Denizens pack and a ring of summoning.
• Spirit Tree: Attack 5, Health 16, Aspects; Ordaniis (Enhance), Yeowynn (Health), Wodren (Soul), A creature defended by this card cannot die while it remains defended by this card, always falling to 1 hp instead. Crafted with a Beloved Friends pack and a Large Spirit Tree Mask.
• Primordial Malevolance: Attack 13, Health 9, Aspects; Wodren (Soul), Freiwynn (Vision), Geogirlaz (Void), You can attack with another card as part of the same action as this card attacking, but this card has that cards attack subtracted from its own for the attack. Crafted with a Disturbed Denizens pack and a Ring of Recruitment.
• Primordial Malevolance: Attack 9, Health 15, Aspects; Yihinren (Form), Byariis (Corruption), Byrginaz (Muscle), This card is Unaffected by other card's Corruption. Crafted with a Sludgeon Delver pack and a Ring of Dispersion.