Title, please let me explain. I know it's a hot topic, but I ask you to read and give feedback anyway with a critical eye.

For the people less in the know-how, Commander is a Magic: The Gathering format pretty much equivalent to Deck Masters, where each deck is led by a single creature and is built around it. It's currently the most played format in mtg and skyrocketed in popularity in the latest years replacing 1v1 formats, thus there is a lot of buzzes and interest surrounding it.

TL;DR First I tackled why EDH is an appealing format, then I went on describing the issues YGO as a game has to make a 1-to-1 transposition, and finally, there is a brief exposition of the rules. Here it's a signature spell (continuous or field), not a creature, that lead the deck.

Introduction

My playgroup has a lot of experience with competitive multiplayer card games. We started with A Games of Thrones LCG 1ed, we switched to multiplayer 2v2 Netrunner when it was discontinued, then we switched to magic EDH/cEDH when that was discontinued as well. Multiplayer card games have been our gigs for the last decade or so.

Now, since our current playgroup has a couple of current YGO players, who tried to sway us into playing YGO, we tried to search for rules online about a multiplayer format that could be somewhat related to that, but multiplayer formats are pretty rare in YGO and the only highlander one we found with decent support was Trinity, but the rules weren't as streamlined as we hoped for. All ruleset made by players we found online seemed to be bad straight-up conversions of the original mtg format into YGO, without understanding or addressing the nuances of the two games.

We were disappointed. So, coming from a long experience with multiplayer card games, sometimes even at a competitive level (to me, in AGoT especially), we tried making our own format and I'd say it works alright. It's still not perfect but is a serviceable starting point to brewing up something on top of it.

Commander Appealing Cons

Our effort was oriented toward replicating these four appealing positives of the original EDH format.

• Multiplayer card games are fun and strategic for combo-oriented games. A layer of complexity that's not there in 1v1 card games is the fact that there are three opponents instead of one, and this is massive! A player can't just combo off in the first/second turn, because there are thrice as many opponents that can interact with interrupts and stop you, so you (as a good multiplayer player) should decide when it's the right time to combo out when the other players are depleted, without overextending if you can't afford to do so. It's a strange "King of the Hill" gameplay that's hard to explain if you don't have a first-hand experience about this; Competitive EDH is a clear example of this and is the direction I'd rather see a YGO commander variant go (as a high-interactive, fast-paced, combo-oriented game).
• Commander offers a new deckbuilding challenge. The format has a single build-around card that you've access to at all times during the game and that can be used as an enabler of strategies since you've always had access to it. To all intents and purposes, it must offer a new challenge in deckbuilding because it should enable new interesting strategies.
• Commander was meant to be a cheap format. While this is not currently true in mtg, since the format was using cards that didn't see much play in competitive mtg, building a deck was penny cheap and drew in a lot of players on a relatively stagnant game. Also, players with a large enough connection can easily build one on the spot because it only requires singles and not multiple copies.
• Commander is a social format. This means, that is easier to bring in new players to the game with a multiplayer game than with a 1v1 card game; then, once they know the rules, make them play another 1v1 format it's just a single step away.

Yugioh Issues

Still, we were aware that there are multiple issues with YGO rules as they currently are. We went back to the drawing board and laid out all the potential issues against our project.

• Who can you attack? A free-for-all format won't work if you're free to attack anyone, because I'd see three players ganging up on whoever has an empty field. We introduced a King of the Hill rule, inspired by the Boss Duel rules.
• Monsters as commanders? It just doesn't work. In YGO all players have access to an Extra Deck with up-to-3 copies of specific creatures they've access to through their gameplay, so it's not very appealing to offer a new creature to put in a new equivalent-extra-deck zone and they won't offer a new deckbuilding channel. We opted to introduce Signature Spells, which are continuous spells instead of creatures and can be used to build your deck if you use them as starters and those offer a big change on how you'd approach deck building.
• Restrictions? It just doesn't work. Restrictions based on attributes, types, archetypes, or a combination of those are just wonky, playgroup fiat, and just unbalanced, so we opted to avoid all restrictions.
• Commander Tax? Since YGO doesn't have mana and tributes would be accessible only in specific strategies, we decided that the cost for recurring a signature spell if destroyed must be a resource everyone has access to, which is paying Life Points. This also plays well with the already introduced concept of the Boss rule.
• Deck Size? This was a contentious point in our playgroup. We agreed that YGO as a game (due to its fast pace and combo-oriented gameplay) should still be more focused than the EDH variant from mtg, so we thought that going upward from 60 cards would have proven an issue; to the contrary, just by introducing highlander rules the deck will lose enough consistency, it would've been difficult to make a deck playable, even considering the access to a free starter/extender as your signature. We considered all options from 30 cards up to 60, but we chose to settle down for 50 cards.

These are the main issues, but there are still a few smaller ones that needed to be dealt with.

• Alternate Win Conditions? This doesn't happen often and we've yet to playtest it long enough, but we introduced a specific rule for it.
• Links/Columns? We wanted this to be as seamless as possible with the current link rules. This is our current multiplayer Playing Field; players share their leftward link zone with the player to their left and the rightward line zone with the player to their right. Column-wise, you share the first and second columns with the player to your left, the third with the player in front of you, and the fourth and fifth columns with the player to your right.
• Ban List? Our first draft was to make all Limited, Semi-Limited, and Forbidden cards be Forbidden. If a card is strong enough to see play as a 1-of in a format with the "Maximum of 3 Rule", in a highlander format we started by putting them immediately on the banlist. Then we started by adding {{Field Barrier}} and {{Prohibition}}, but we're still brewing around other popular continuous or field spells to see how much broken they are.

Signature Spell Format rules

All things considered, the rules are pretty simple. The format is meant to be a 50 cards highlander format, headed by an always-available continuous/field spell (to use as your starter and as a build-around) and with small adjustments to make it work as a free-for-all multiplayer game.

• 8000 LP: Each player starts with 8000 Life Points.
• 49 1 Main Deck: The Main Deck can have 49 cards, including their Signature Spell. The Extra Deck can have 10 cards. Decks must follow the "Maximum of 1 Rule".
• Signature Spell Rules: Each deck has a continuous spell or field spell designated as Signature Spell. Whenever your Signature Spell leaves the field and is sent to the graveyard, hand, deck, or banished, is placed face-up into the Extra Deck instead.
  • Setup Rule: Before starting a Duel and before shuffling their main deck, duelists set their signature spell aside and shuffle the remaining 49 cards. After they've drawn their starting hands, duelists activate their signature spell in their field zone.
  • Spell Tax Rule: A player can set and activate their signature spell in the Field Zone from the extra deck if they pay 200 LP for each time the spell was sent in the extra deck that game.
• Free-for-all Rules: It's a free-for-all game with 4 players that follows the "Boss Rule", "First-Turn Draw Rule" and "No First-Turn Attack Rule". Turns are played clockwise and the first is determined by dice roll.
  • Boss Rule: The player with the highest LP (or tied for it) is a Boss. If you're a Boss, you can attack whoever you want; if you're not a Boss you can only attack the boss.
  • First-Turn Draw Rule: The player who takes the first turn of a Duel does conduct a normal draw during their Draw Phase.
  • No First-Turn Attack Rule: No player may attack on their first turn.
  • Field Rule: Fields, except for Link Zones, are not shared. The top 2 half-Zones (7) are the Extra Monster Zones. The one on the left is shared with the player sitting on your left; the one the right is shared with the player sitting on your right.
  • Alternate Win Condition Rule: If a non-Boss player achieves an alternate victory condition, inflict 8000 damage to all bosses instead.

Oof, this was pretty long. Our playgroup will proceed with playtests in the incoming weeks, but I'd love to hear from you if this is well-thought-out and if there are glaring issues still.

Thank you very much for reading this!