Does Legends of Runeterra Need RNG? Explaining Randomness in Card Games

The random aspect of card games is often what makes them fun. It provides thought-provoking moments where your decision-making will determine a victor. But what exactly is randomness?

Since the dawn of the genre, card games have involved randomness to varying degrees. There is always an element of the unknown. Which cards does my opponent have? Which cards could they have? Can I make them think I have cards that I don’t have?

The random aspect of card games is often what makes them fun. It provides thought-provoking moments where your decision-making will determine a victor. It allows players the luxury of bluffing or representing actions they may not be able to take. It creates a detective out of all of us. But what exactly is randomness?


Randomness is a term used to describe the combinatory effects of variance and uncertainty. Variance is the spread, or range, of potential outcomes that individual actions might result in. Uncertainty, on the other hand, is a lack of information or knowledge regarding those outcomes.

For example, suppose you have a list of colors and you want to select a color from the list by rolling a die. In this case, the full list of potential colors is the variance. The uncertainty is portrayed by your lack of knowledge about which number the die will land on when rolled.

When it comes to card games, game designers and players alike have various ways to tweak the levels of variance and uncertainty that can be experienced while playing the game.

Playing With Variance

With every card game, there are two sources of variance involved before a match even starts: your deck and your opponent’s deck. Before the game starts, both you and your opponent decided on which cards to put in your respective decks. 

Deckbuilding provides players with the ability to limit variance for their benefit. They do this by including multiple copies of the same card in their deck and keeping the number of different cards to a minimum.

Developers can adjust a game’s variance by adding new cards to the card-pool. As more cards are added to the game, the set of cards you can play in a given color, class, or region increases. Not only that, but individual cards themselves will impose variance onto particular matches.

Most often these effects center around a specific pool of cards to limit variance while introducing some uncertainty into games. Cards like Piloted Shredder in Hearthstone and Pilfered Goods in LoR are good examples of cards that have varying effects depending on a limited pool of cards. Shredder’s effect range is “all 2-Cost minions”, while Pilfered Goods has a spread of “all cards in your opponent’s deck that have yet to be drawn.”

Random effects of this nature are often healthy for play experience different from match to match. They keep players engaged and allow us to feel those “I can’t believe that just happened!” moments that card games provide. But an excess of these effects can cause players to feel that their decisions don’t matter in changing the course of a match.

Embracing Uncertainty

Like variance, uncertainty is a lever that developers can pull to adjust the randomness in a card game. This can be done in numerous ways such as limiting random outcomes and revealing information to players each match.

In some games, like Magic: The Gathering, what is in your opponent’s deck is entirely uncertain from your point of view before the game starts. In other games, like Hearthstone and Legends of Runeterra, you are given information about your opponent’s deck as soon as you are paired against them (class choice or region selections). This information reduces the uncertainty around what you might be up against and informs a player’s mulligan decisions and other actions throughout the game. 

By nature, players look to limit uncertainty by determining what cards an opponent has access to in their deck and, more importantly, in their hand so they can make informed decisions about what to play next. 

Every card game has inherent uncertainty: What card will I draw next? Does my opponent have a card that can punish me for this play? Does my opponent know that I have this card? If you have ever played a card game you have asked yourself one of those questions. They are simply part of the genre. As such, it can be troublesome when a game’s mechanics impose further levels of uncertainty into matches.

‘Balance in All Things’

Too much randomness can be harmful to card games and how they feel to play. Ultimately, the genre should reward excellent play and maneuverability. It should reward the strategic-minded and value those who make educated and thoughtful decisions, from deckbuilding through gameplay.

But the genre also needs to allow for randomness. It needs to provide outs for players who find themselves in a bad matchup. It needs to remind players that they have a chance to win even when behind if they can outsmart their opponent.

Without any randomness, certain matchups would 100-0 in favor of a specific archetype and that would simply be unfun. Designers tweak the levels of variance and uncertainty to allow for fun play patterns and reasonable randomness that makes the game more enjoyable to play.

Unfortunately, they don’t always get it right and it can be easy to overdo randomness in this genre; however, digital card games have the benefit of balance patches and live adjustments to cards that have been “printed” so there is always room for improvement.

How do you feel about randomness in card games? Do you think it helps? Would you rather see less of it? Let me know in the comments or reach out directly on Twitter @RanikGalfridian to further the conversation!


Ranik is a strategy fanatic and lover of card games. Before switching primarily to Legends of Runeterra he played Magic: The Gathering for eight years where he enjoyed dominating opponents with slow control decks. Now he focuses on creating Legends of Runeterra content for all players and enjoys discussing strategy and deckbuilding on Twitter @RanikGalfridian.

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