On dual-class cards

Spoiler: Update 1.6 will feature dual-class cards. Well, I hope. Game design of dual-class cards is quite hard, so I'd like to post about the challenges I'm facing. But to understand dual class cards...

The Origins of the Class System

The class system begins from Spectromancer, the game that started it all. In it, you could choose between classes to play,such as Warrior Priest, Sorcerer, or Chronomancer. Each class had 8 cards, 1-8, and you would be dealt 4 of them for your deck, similar to the deal of the basic cards.

This wouldn't do for me. I wanted you to be able to customize your deck. But to be able to mix and match cards freely would cause some balance issues. There were some cards that could end the game as soon as they were played. For example, mana dork, a1, mana dork, divine justice ends the game right there. Similarly, drain souls could end the game if you overcommitted, and there was the aggression of illusionist (which was much more evoker-like than the current iteration.) These cards were balanced by the fact you could play around them; after all, there were 8 cards per class, and your opponent would have four of them. If you could mix and match cards at will, it would be unrealistic to play around them all.

This led to the design of the first sigil system. The sigil system was there to limit how many effects you had to play around. For example, cards that could get a huge advantage early like the aforementioned divine justice had the shockwave sigil. Paticularly powerful effects like drain souls could require two of the same sigil, while an effect like angel of war could have a sigil for the damage and a sigil for the healing.
You could trade card slots for sigils, or sigils for extra life. (Or other effects, which eventually became a reality when runes were added to the game.) However, it soon became clear that the UI design for the grid of sigils and displaying which sigils you had to the opponent was unworkable.

The next system was the attribute system. You'd have a fixed number of attribute points. Attribute points could be spent on CON, which gave starting hp, or other attributes, which entitled you to use certain cards in your deck. A card like angel of war could require two attribute types: one for the healing, and one for the AoE.

But then I realized you didn't need an attribute selection box. After all, you could just put the cards you wanted in your deck, automatically assign attributes to so that your cards were needed, and the rest in CON.

This was essentially the first class system for Aethermancer, back in the single-player client days. The attributes got replaced with class names, for example Angel of War required warrior and cleric levels, (warrior + cleric = warrior priest / paladin), and instead of assigning attributes to stats, you'd buy class levels with HP.

Over time, the classes got restructured (why does Mech and Warrior both do AoE? better make that banisher) and simplified (instead of a card requiring Mech 4, it would just required Banisher, which costed a fixed amount of hp). This is where the class system is today, and it has served its purpose well.

Limitations of the Class System

The class system ran into some limitations though. Each class had its own effects it "owned", but I wanted to make some cards that had multiple effects. I eventually decided that some effects were available for share if the rate was inefficient enough (like damage AoE), while some effects would be class-exclusive (like freezing a player). This made Holy Nova possible. After all, still only banisher has a stone rain cheap enough and does enough damage that it fills the "shockwave" effect of Creating Big Advantage over mana dorks.

But with the advent of Lifelink as a mechanic, there were some designs I wanted to make that would feel like a pie break in either class. Big lifelink damage to a creature. Big lifelink damage to a player. Higher ranks of the removed Holy Jolt and Weakening Jolt. A modal 6 mana spell that could either be used as a tornado or gain 25 life. So here's the motivation for dual class cards.

How It's Handled in Other Games

I'm not the first to want to make dual class cards in my game. The equivalent to classes in my game is colors in MtG. MtG makes a distinction between "hybrid" and "gold" cards. A hybrid card does something either color can do. A gold card does something both classes can do. Many card games have followed MtG's lead and made cards with multiple color requirements.

However, due to the way the class system works in aethermancer, if I did that, I might as well be printing it into universalist, which means that what classes the card was ends up not mattering.

Is there an example of a card game with similarly unmixable classes? Hearthstone!

The most notable dual-class card I can think of is Shroomscavate. This gives a card Divine Shield and Windfury, and can be played in either Paladin or Shaman. As we all know, Shroomscavate was a balance disaster, so lesson learned not to repeat that.