A Magic sideboard is not a pile of powerful cards kept for emergencies. It is a structured reserve that corrects specific matchups between games without dismantling your main plan. Every slot should answer three questions: what problem does it target, when does it come in and what leaves the main deck?
This guide focuses on Constructed matches with multiple games. First stabilise your mana curve and mana base. A sideboard refines a functioning deck; it cannot repair a list that fails to execute its own plan.
What the rules allow
In Constructed, a sideboard may contain up to fifteen cards. The usual four-copy limit applies across the main deck and sideboard together, except for basic lands and cards whose text allows otherwise. Before the first game of every match, both zones must match the registered configuration.
Between games, you may exchange any number of cards as long as the resulting main deck and sideboard remain legal. The exchange does not have to be one for one. Your main deck must still meet its minimum size and the sideboard cannot exceed fifteen cards. Event-specific rules always take priority.
| Moment | Action | Check |
|---|---|---|
| Before the match | Present the registered configuration | Main deck and sideboard complete |
| After game one | Make planned changes | Legal size and copy limits |
| Before the next match | Restore the original list | No card left in the wrong zone |
Build from problems, not card names
Start with situations that stop your deck from working. Aggro may need tools against life gain or sweepers. Control may need cheaper interaction against fast openings. Graveyard strategies need answers to hate pieces as well as a plan when the opponent attacks the graveyard.
Group problems into five families: difficult permanents, graveyard engines, very fast decks, slow value engines and combos relying on one key piece. Flexible cards that cover several families are valuable, but narrow answers remain justified against decisive and common threats.
The four-column Poke-Geek matrix
- Target: name the problem rather than one fashionable deck.
- Card in: record the quantity and when it must matter.
- Card out: remove a weak, slow or poorly positioned card.
- Side effect: recheck curve, coloured sources and lost synergies.
This prevents a common failure: adding many answers while removing the cards that let the deck win. The transformed list must still function as a deck.
Narrow or flexible answers?
A narrow answer can be excellent against exactly one target and blank elsewhere. A flexible answer is less dramatic but enters in several matchups. Mix both. Reserve narrow slots for important, frequent problems and use flexible cards when the local field is uncertain.
Check the real mana cost too. A two-mana spell is not early interaction if its colour requirement is rarely available on turn two. Revisit the mana-base guide after every substantial change.
Write the in-and-out plan
Before the event, make short plans for broad categories such as aggro, control, graveyard, artifacts and enchantments, or combo. Note what enters, what leaves and why. On the play, pressure and tempo may gain value; on the draw, cheap interaction can become more important. Treat that as a question to test, not an automatic rule.
Fifteen-card checklist
- Every card answers an identified problem.
- Every incoming card has a planned outgoing card.
- Main deck plus sideboard respects copy limits.
- Coloured costs match the mana sources.
- The win condition survives the changes.
- Every card is legal for the format and event.
- The original configuration is restored before each match.
Test without overreacting
Play short sets and record whether a sideboard card was drawn, castable and relevant. Do not dismiss it because it was not seen, or crown it after one win. Also measure the cards you removed: too many changes can reduce threats, lands or synergy pieces.
For combat decisions during testing, use our guide to attackers and blockers. Magic products and accessories are grouped in the Poke-Geek Magic collection.
Common mistakes
Copying fifteen cards without their context
Another list may expect a different field, use a different mana base or contain a transformation plan that your deck lacks.
Bringing in too many answers
If you remove too many proactive cards, your deck loses its route to victory. Define a sensible maximum for each matchup.
Forgetting the original configuration
Use a clear decklist and count the sideboard before every new match.
Confusing Constructed and Limited reserves
Draft and Sealed build their reserves differently. Our Draft versus Sealed guide explains that context.
A repeatable method
Start with five matchup families, assign no more than three cards to each and look for overlap. Write the exchanges, test the post-board curve and keep only notes that remain useful across sessions.
Your next step: lay out your fifteen cards, name the problem each one solves and identify a corresponding card to remove.