1. All players use the same library, hence communal. If an effect would cause players to manipulate the library (draw, scry, put cards on bottom) it is done so in turn order starting with the active player.
2. Opening hands and maximum hand sizes are both four. NO mulligans!
3. All players have infinite mana of all colors and types at all times. That mana has the caveat that it can only be used to cast up to one spell per turn (note you can still activate abilities and cast spells that require no mana to cast). This is my personal take on the classic/modern Type 4 rules. Normal Type 4 rules state that players can only cast one spell per turn (old) OR players can cast only one spell per turn unless they use an alternate casting cost (new). I find my rules are easier for unfamiliar players to understand.
   3(a). If a player would generate mana (ex. from a treasure token) that mana is separate to the infinite mana in that player's mana pool; meaning the generated mana is not restricted to the "one spell per turn" limit. So if a player has already cast their spell for the turn, but has a treasure token, that player can spend the treasure token to cast an additional one-mana spell (such as Brainstorm).
4. Players have their own graveyards but share an exile pile (except for a temporary exile pile for cards that can be cast later - like cascade, Gonti effects, etc.).
5. If Player B gains control of a card "owned" by Player A, Player B is now the "owner" of that card; should it go to a graveyard, it will go to Player B's graveyard. This is another rule for my stack, and not a typical among other stacks. Keeping track of card ownership leads to unnecessary complexity in a shared card pool. Card examples: Aethersnatch, Memory Plunder, Blatant Thievery
6. Multiple instances of infinity is awarded to the "defender". The "defender" is whoever's FIRST INSTANCE of an ability is activated last.
   Example 1: Player A activates Flowstone Overseer targeting Player B's Armored Guardian. Player B then activates Armored Guardian. Player B is the "defender" and will successfully protect the Armored Guardian.
   Example 2: Player A casts a removal spell on Player B's Armored Guardian. Player B activates Armored Guardian in response. Player A responds by activating Flowstone Overseer. Player A will be the "defender" beceause Player A has the last FIRST INSTANCE of the ability on the stack. Thus the Armored Guardian will put into the graveyard.
7. It is a free-for-all.

1. No shuffle effects. Don't want to waste time shuffling.
2. No double-faced cards. Annoying to desleeve, forget what the other side does, forget to flip them back.
3. Removed most one-shots (ex: firebreathing, shade pump).
4. Removed most of the explosive card draw (ex: Opportunity). Also removed most open-ended card draw (ex: Phyrexian Arena, Temur Ascendancy).
5. No reserve list cards.
6. No Morph, Manifest, Cloak, Disguise - this is just an quality of life (play) restriction.
7. No Future Sight, Bolas’s Citadel, Sensei’s Divining Top like abilities that gives a player constant vision/manipulation of the top card of the stack. It slows the game down. Note, there are still one-time scry, surveil, fateseal effects, as these are interesting when everyone shares a library.

UNLISTED CARDS FROM GAVIN'S UNKNOWN EVENT
Call Up Emrakul to Help
Sword of Fire and Ice and War and Peace
Force of Rowan