How do you test and improve a deck?

A deck for Riftbound: the League of Legends trading card game is not finished on the day you build it. A list looks different once it is shuffled and dealt, and only games show where. Riot's deckbuilding primer, written by Game Director Dave Guskin, gives the method: build a rough draft, play it against friends or at your local store, ask what was strong and what was weak, and let the answers shape the next version.

What can you test before you play a game?

You can test how the deck starts. In a Main Deck of 40 cards only 39 are shuffled, because the chosen champion waits in the Champion Zone, and every game starts with four of them in your hand. Deal yourself four and ask what you would send back with a mulligan. If hand after hand holds nothing to play in your first two turns, the deck needs more cheap cards. The sample hand in the deck builder does the shuffling for you, and the Energy curve on the same sheet shows how many cheap cards the deck holds.

Then play a few turns alone, a habit card players call goldfishing. Channel two runes and draw a card each turn, play what you can and see on which turn the deck does what it was built to do. A deck like the Origins Champion Deck: Jinx shows why this matters, because it empties its hand on purpose: Chemtech Enforcer discards one card when it is played and Jinx, Demolitionist discards two. Flame Chompers can be played for a single Fury Power when you discard it, and Rhasa the Sunderer costs 10 Energy, one less for each card in your trash. Only test games show how early Rhasa really comes down in such a deck.

Who should you test a deck against?

Test against other players, and against more than one kind of deck. Ready-made decks make good test opponents, because they play the same way every time. The four decks of Proving Grounds pull in different directions. The How to Play booklet in the box tells the Annie player, who leads with Dark Child, to clear the way with spells and sweep in to take battlefields, and the Master Yi player, who leads with Wuju Bladesman, to bide their time in the early game until their fierce warriors arrive. The Lux deck, led by Lady of Luminosity, waits behind cheap units for its expensive spells, and the Garen deck, led by Might of Demacia, sends a whole army to conquer. A deck that beats only some of them has a weakness worth knowing.

Play from both seats as well. In a one-on-one game the player who goes second channels three runes on their first turn instead of two, so a deck can feel quite different when it starts second. Once the deck works at home, a weekly Nexus Night at a store brings opponents you did not choose. When no opponent is near, fan-made simulators can fill in, as the article on playing Riftbound online explains.

What should you watch for in a test game?

Watch the cards more than the result, and write a few lines after each game while you still remember it.

• Cards that stayed in your hand. A card you could not pay for, or never found a good moment for, is the first one to cut.
• Turns with nothing to do. Unused runes on an early turn point to too few cheap cards, and an empty hand late in the game points to too little card draw.
• Power of the wrong domain. If you often have the Energy for a card but not the Power of its domain, the split of your 12 runes may be off.
• How the game was lost. Note the card or the plan that beat you, so you can look for an answer to it.

How many games does it take to judge a card?

More than one or two. In a one-on-one game without a mulligan, you have seen seven cards of your Main Deck by the Main Phase of your third turn: four in your opening hand and one in each Draw Phase. A card you play three copies of is among those seven in only about 46 percent of games, and a card you play once in about 18 percent. A card that did nothing in two test games may simply never have been drawn.

So judge a card by what it did when you had it, not by whether you won. Play several games before and after a change, against the same opponents where you can.

Which cards should you change, and how many at once?

Change two or three cards at a time, so you can tell which change made the difference. Cut the cards your notes name most often, and replace them with cards of about the same Energy cost unless the cost itself was the problem. Keep the Main Deck at 40 cards: the primer and the booklet both advise against a bigger deck, because every extra card makes your best cards harder to draw.

The primer adds one pointer for the cuts themselves: when in doubt, play more units, since you need units to contest battlefields. Change the runes the same slow way, one rune at a time, once your notes show one domain coming up short.

Two checks help when your notes point at the whole list instead of single cards. A hand full of cards you cannot pay for suggests that the Energy curve leans too high, and a list with few units may break from the usual mix of units, spells and gear, which leans on units. A deck from a box, such as a Champion Deck, is a good place to practice these changes, because it is meant to be upgraded a few cards at a time.

With an account, you can save each version of a deck in the deck builder as a private deck under its own name, so you can compare versions and go back when a change makes the deck worse.

Can you change a deck during an event?

Only a little. Even at a casual event that asks for no decklist, players are expected to keep the same deck for the whole event unless the organizer allows a change. At Competitive and Professional events you register the deck before the first round, and the list cannot change after that. Make your changes between events, and bring the version you tested.

Where an event allows a sideboard, it holds up to 10 cards that you swap one for one with Main Deck cards between the games of a match, never before the first game. Test those swaps at home as well. The Tournament Rules on Riot's Rules Hub allow no proxies at any event, other than an official one that a head judge issues to replace a card that cannot be used (rule 419.2). A card you tried out with a stand-in at home therefore has to be the real card before you play it at a store. Single cards come from local game stores and from online marketplaces: Cardmarket in Europe, TCGplayer in the United States and CardTrader on both sides of the Atlantic.

A ready-made deck can also hold banned cards. The Jinx Champion Deck holds three Fight or Flight, three Scrapheap and the battlefield Reaver's Row, all on the banned list of Constructed. At a casual event such as Nexus Night the deck may keep them only while it is played exactly as it comes in the box (rule 601.2.d.2), so changing a single card or adding a sideboard means replacing those seven cards as well.

The shared decks show complete decks other players have built, and Create copy opens any of them in the deck builder as a starting point of your own. Once a version of your own works, you can send it to a testing partner as a link or as plain text, and the same list is what a Competitive event asks you to register, as the article on sharing or importing a decklist shows.