Villain Basics
To start let's look at two cards from development: Feedback and Goblin Mage (as you might guess, the art on the cards is not even close to final).
Let's first explain the numbers on the cards. There are five positions for values on the cards, from left to right these are:
-Card Cost: The leftmost symbol (the dollar sign is temporary, I promise). This value indicates how much the card costs to be played. These costs can be payed by exhausting energy attached to your Hero cards.
-Point Value: The middle left symbol. This value indicates the points earned for defeating this villain card.
-Hand Size: The middle symbol. This value indicates the size of this villain's combat hand (a lot more on this later in the article).
-Magic Power: The middle right symbol. This value indicates the maximum cost of cards that can be played by this villain.
-Health: The rightmost symbol. This value indicates the amount of damage that must be done to this card before they are defeated.
A demonstration
Now, let's examine the process of how villains interact. You're playing Mahoujo with a friend and they play Goblin Mage. Now they declare that they're attacking Goblin Mage. Since there are only two players, the non-attacking player (you) automatically controls the defending card. (Goblin Mage.) Put your hand down and draw 3 cards out of your deck. These cards are your combat hand. During the battle you can cast spells from your combat hand, and discard cards to use the villain's abilities. Let's say that one of the cards you've drawn for your combat hand is Feedback.The ability Ruin has a Chant requirement, so you must wait through two rounds before it can be cast. Because your opponent will probably defeat the Goblin Mage before you can complete the chant requirement for Ruin, you decide to cast Blast instead. To use Blast, you discard one of the cards from your hand to deal 3 damage to your opponent's Hero. Now they play a Magic Spell from their hand and exhaust their energy to pay for it. You take advantage of the situation and play Feedback to block the spell and deal damage at the same time. You're allowed to cast this spell because the cost (of five) is less than or equal to the Goblin Mage's casting power (of eight).
Next action you take you discard your last card and deal 3 more damage to your opponent's Hero. Due to the unexpected Feedback card your opponent has spent all of their energy without defeating the Goblin mage so they declare that they retreat. You don't have any abilities you can play so the battle ends.