Here are some deck building tips straight from the Dev Team:

• Always aim to use all 20 points for your deck. There is no benefit to running a deck under 20 power.
• Choose the deck archetype that suits you.
• Single element, aka mono, relies on special abilities that synergize with cards of the same element to be effective. when building mono, pick abilities that benefit cards of the same element.
• Multiple elements, aka multi, brings cards of all elements and can use abilities that don’t rely on element synergy to be powerful, or not use any ability. Multi is flexible and can take advantage of all element tiles, but has less abilities that directly benefit it.
• Cheap cards are important too! Using cheap (aka fodder) cards allows you to bring more powerful cards, and lets you start the game with cards that you can easily take back. A good mix of cheap, average and expensive cards can be more effective than a deck made entirely of average-cost cards.
• Remember that what matters in the end is who has the card, not how powerful it is. It’s easier to put a cheap card in a position where you can take it back if the opponent flips it, than it is to make sure a card is so strong the opponent won’t take it.
• Always aim to place cards in a way where an even number of weak sides can be reached by cards you own.
• Try to make sure your cards can retake each other. try to imagine how you would play each card and where the opponent could capture it from, and how you can capture the card back when your turn arrives.
• Try to have at least one strong option in each direction. it’s possible to build effective decks with blind spots, but it’s much harder to deal with situations your opponent will create if you don’t have an answer for each side.
• Consider your rival’s ability when building a deck:
  • Zetterburn: Zetterburn can remove any debuffs from your own cards, and any buffs from opponent cards. He’s also a very powerful card on his own, ideal for taking powerful cards. use him alongside abilities that change numbers to end up with a powerful, hard to retake board, or to weaken the cards you can’t take.
  • Maypul: Maypul’s chain requires careful planning. plan your deck and play your cards always trying to draw a chain, and make sure you can start the chain with her. you can also use her to claim cards that are locked away. taking one or two extra cards that can’t be taken back by the opponent is more valuable than hoping you can capture half the board at the end of the match
  • Absa: *basically the same thing as maypul*. use elemental tiles to change numbers in clever ways to open up new spots to match. a card that doesn’t match with absa might be able to match if the card is placed on a -1 tile, for example.
  • Orcane: Orcane can capture cards through walls. as such, he’s really good at taking cards that have their weak sides pointed to walls. capturing cards from a distance also means you can take a card for yourself while still leaving an even number of sides open, forcing your opponent to make a tough decision
  • Clairen: you can use clairen in two ways: either you get her surrounded by weaker cards so she can’t be captured and they’re guaranteed to be yours when her ability activates at the end of the match, or you use her plasma field to limit your opponent’s options. depending on how the field is played, it can completely disable certain rivals from being played. Also, remember that using an elemental ally on Clairen will activate the plasma field.
  • Etalus: Etalus’ ability makes it so cards can’t be taken anymore, and disables any abilities they might have. one common strategy with etalus is using him to capture one or two cards of different elements to make it easier to set up your avatar plays. you can also use him to capture cards without worrying about the opponent taking them back.
  • Wrastor: Wrastor’s numbers aren’t particularly impressive but his ability more than makes up for it. any card moved by the tornado will attempt to flip cards after being moved, so you can either get a ton of flips in a single play, or accidentally backfire if you’re not careful. you can use the tornado to create holes in spots that aren’t reachable anymore, allowing for captures that no other card in the game could make. and remember: you can use *any* card after the tornado, you don’t have to use wrastor!
  • Sylvanos: Sylvanos is made for mono decks, but can fit into any element. make sure to bring at least one homefield card with him. sylvanos can be played early on to force the entire field to shift towards your element, or later to get a lot of captures. make sure your deck can always be taken by sylvanos from one direction so he can take them back, and don’t leave sylvanos for too late or you might not be able to use his ability at all.
  • Forsburn: Forsburn’s smoke lets him hide cards that don’t have abilities (and cards that don’t activate their abilities). use this to make the opponent second-guess if they can capture a card or not, causing them to overspend their resources on a capture. forsburn can also teleport to a smoke tile and capture cards again at the end of your turn if you own him, making him capable of threatening the opponent’s plays even after being placed.