This post is part of a series I’m writing about my efforts to create a Magic: the Gathering draft bot. The series will be grouped under the “draft_bot” tag.
Summary: In this post I’ll go into some of the basic concepts of MtG and drafting, which are prerequisites for the following posts. You can probably skip this one if you’re already familiar with Magic.
Introduction to MtG Drafts
Magic: the Gathering
Magic: the Gathering is the oldest trading card game in existence; in my opinion, it’s also the best game ever made. Throughout the course of a game, players build up resources and use those resources to cast spells and creatures (minions that can attack your opponent or defend against them). I won’t go into all the rules here, as the game is notoriously complex; check out the official intro page if you are interested.
For now, you just need to know that in order to play a game of Magic, you need a deck of cards to draw from. This presents a problem for new players – if you’re new, you don’t own any cards. Where to start?
Limited Formats and Drafting
Magic elegantly solves this problem with the concept of limited formats. These are game formats that don’t require players to come ready with a deck: instead, they start with a subgame in which players build their decks using randomized sets of cards, or “packs”. (These packs are sold as sealed product by Wizards of the Coast, the company that owns the game.)
Draft is one of these limited formats. There are many possible types of draft, but the most common one works as follows: A group of 8 players sit in a circle – each one opens a pack of 15 randomized cards. After taking a card, each player passes the remaining cards in their pack to the player next to them. Each player repeats that process as the packs are passed around until no cards are left. This whole process happens 3 times (each player opens 3 fresh packs and passes them around the table). By the end of the draft, the players have enough cards to build a deck and start playing. See the official description by Wizards of the Coast here.
Draft Formats
New MtG cards are usually released as part of a larger “set” of cards that are meant to be drafted together. Players will often refer to a group of cards meant to be drafted together as a “draft format”. Game designers at WotC create these draft formats with the intention of creating a fun environment where players can draft a diverse set of possible decks that interact in interesting ways.
Draft Strategy
For each player, the draft subgame consists of about 40 “pick” decisions: given the pool of cards I already have and the cards I have already seen in the draft, which of the cards should I take out of the pack in front of me?
Consistently drafting well is quite difficult; there’s a surprising amount of complexity behind this subgame.
Card strength
This is probably the simplest factor to evaluate when making a draft pick. Some cards are simply more powerful than others – that’s the way the game was designed. Players are (naturally) trying to pick the most powerful cards available to them. It’s common for players to take the one “rare” card in the pack as their first pick, since rares are often much stronger than the average card.
Community members will often release draft guides for each draft format with their power rankings of all the cards available in the format (for example, this DraftSim tier list for BRO).
Synergy with pool
For each draft pick, players must consider how well the pick synergizes with the cards that they’ve already picked (their “pool”). This is probably the most important factor for the majority of picks – there are several related sub-factors that determine a card’s synergy.
Colors
Again, I’m trying not to go too deep into the MtG rules here, but it’s nearly impossible to talk about drafting without touching on the concept of color. Mana is the most important resource in the game – it’s how you pay for playing your spells and creatures. Mana comes in 5 colors (or colorless); individual cards will tell you how much of each color of mana you need to pay to cast that card (check out the intro page for some examples).
Color is an important tool for the game designers to restrict and differentiate the types of MtG decks that are possible. It’s difficult to play lots of cards with different color requirements in the same deck, since cards that produce multiple colors of mana are rare or have various downsides (they will make your deck slower and less consistent). This means that you can’t just jam all the best cards together into a deck – you have to take their color requirements into consideration and make sure that you’ll actually be able to cast your spells.
This matters a lot when drafting. Players should usually pick cards in similar colors to cards they have already picked. The more cards one already has in a particular color, the stronger the “pull” to pick more cards of that color. By the third pack, players will often pass up on strong cards if the color requirements don’t match up with their pool.
Archetypes
Draft formats are often designed around specific deck archetypes: for example, there might be an aggressive, creature-focused red-white deck archetype in addition to a slower, artifact-themed blue-white archetype. Savvy players will be drafting towards one of these archetypes, and will make picks based on what archetype their pool is trending towards. While archetypes are often associated with certain colors, note that they are not the same as those colors – in the case of the red-white and blue-white archetypes example I just mentioned, there might be white cards that are strong in one deck but not the other.
Deck structure considerations
Successful draft decks usually have a particular structure – a rough number of cards of each mana cost, a rough number of creatures, a rough number of removal or interactive spells (this post goes into more details near the bottom). Savvy players will be drafting towards this ideal deck structure, and will make picks based on what their pool is missing. For example, if their pool already contains 16 creatures but has no removal spells, they might prioritize taking a strong removal spell above all else; if their deck is short on cheap creatures, they might prioritize that instead.
Reading the draft
Staying open
A common draft failure mode, especially among beginners, is committing too strongly after the first few picks of the draft. Early in the draft, there’s a lot of value in flexibility. Drafters who “stay open” to new colors or archetypes often end up with better decks; this is because they end up in a better position to pick up strong cards that get passed to them later on the draft.
Making flexible early picks can mean a bunch of different things:
- Picking cards that are generically powerful in multiple types of decks, rather than requiring a certain archetype
- Picking cards with less restrictive color requirements
- Picking strong cards even if the pool doesn’t have any cards in that color yet
Of course, the longer the draft goes on, the less valuable flexibility becomes. There is less upside in speculating on future picks (since there are fewer picks left), and there is a higher risk of “wasting” your earlier picks and ending up with a nonfunctional deck. Determining exactly when to commit during a draft is a subtle skill that takes a lot of experience to master.
The open lane
A skillful drafter will be able to determine the “open lane” at the table based on information gleaned from passed cards. The open lane is the archetype that is underdrafted, meaning that other players are mostly not picking from that archetype. In the open lane, strong cards from that archetype will basically fall into the drafter’s lap – there’s little to no competition for them!
There are several methods for trying to find the open lane:
- Noticing “wheels.” A card wheels when it goes around the whole table back to you without getting picked. If it was a strong card, that could indicate that other players are not picking from that card’s color / archetype.
- Counting colors. The more quality blue cards you see coming your way, the more likely blue is to be open.
- Signposts. There are certain cards that pull very strongly into certain archetypes; these are sometimes referred to as archetype signposts. If the players to your right just passed you one of those, you can infer that they’re probably not in that archetype.
Again, this is a subtle art. Skilled drafters will be able to adapt to signals in real time and are usually rewarded for it.
Motivations
While not as complex as MtG itself, the draft subgame is quite difficult to play optimally. There are a lot of pieces of information that need to be considered at once, and players need to be ready to make subtle tradeoffs across multiple axes.
I decided to focus on training an ML model to draft because it’s an easy task to represent abstractly, but humans tend to find it quite difficult. I personally would like to improve my drafting, and I’m hoping that in the process of training this model and applying it to my own drafts I’ll become a better player!
Scratch Space 