Elder Dragon Highlander is a Magic: The Gathering variant which provides a way of encouraging casual, interactive games with a low barrier to entry while still requiring good deck building skills. It can be played 1-on-1 but is usually multiplayer.
This page details the official rules common to most groups. Local groups often play with house rules, but this consensus version exists so that players know what to expect if they join an edh game outside their local play area. In particular, after-hours EDH games at Pro Tours and Grand Prix use these rules.
Deck Construction Rules
Players must choose a legendary creature as the "General" for their deck.
Players may choose any legendary creature as their general. Two players in the same game may choose the same General, and other players may include that card in their Deck even if it's not their General. Generals are subject to the Legend rule just like any other legendary creature; multiple copies of the same creature (whether General and non-General) will all be put into the graveyard (or command zone) as a state based effect.
The General is the principle around which an EDH deck is built. It is more easily available than other cards in the deck, and EDH decks will ususally want to leverage their General's strengths in their plans. It is not, however, guarenteed to be available at every point in the game so EDH decks should be able to function without it for a time.
The General's mana cost defines what colour of mana symbols may appear on cards in the deck.
Coloured mana symbols which may appear in an EDH deck are restricted to the colours appearing in the General's mana cost. Lands whose type includes swamp, island, plains, forest and/or mountain (e.g.: basic lands, shocklands, dual lands, Shadowmoor special-basics, etc) DO contain the corresponding mana symbol(s) as per CR 305.6. As such, they may not appear in a deck unless the General is of the corresponding colour(s).
While Hybrid mana symbols may be played with either colour mana, they count as both colours. As such, they may only be played with a general which is ALL of the hybrid mana symbols' colours.
Basic land words (swamp, forest, etc) in the text box of a card do NOT represent a coloured mana symbol. They are not restricted to generals of the same colour.
A deck may not generate mana outside its colours. If an effect would generate mana of an illegal colour, it generates colourless mana instead.
An EDH deck must contain exactly 100 cards, including the General.
With the exception of basic lands, no two cards in the deck may have the same english name.
EDH is played with vintage legal cards, with two exceptions:
cards are legal as of their set's prerelease
Shahrazad is legal for play in EDH
The start of game procedure for EDH is as follows:
Players announce their choice of General and move that card to the command zone.
Players may then sideboard if the optional rule for sideboards are being used.
Each player draws a hand of seven cards.
Players may mulligan, using the modified "partial paris" method (detailed below)
Being a General is not a characteristic[MTG CR109.3], it is a property of the card. As such, "Generalness" cannot be copied or overwritten by continuous effects, and does not change with control of the card.
If a player has been dealt 21 points of combat damage by a particular General during the game, that player loses a game
While a General is in the command zone, it may be cast. As an additional cost to cast a General from the command zone, its owner must pay 2 mana for each time it was previously cast from the command zone.
If a General would be put into a graveyard or exile from anywhere, its owner may choose to move it to the command zone instead.
Players begin the game with 40 life.
Generals are subject to the Legend rule; they will be put into the graveyard or command zone at the same time as any other Legendary creatures with the same name.
The official rules are complied here http://www.dragonhighlander.net/rules.php
Partial Paris Mulligan rule
Because EDH games are long and usually not played in multigame matches, EDH uses a modified mulligan rule designed to aleviate mana-light hands without significantly increasing the odds of finding individual cards. This is also known as the "Brittany" mulligan rule.
In turn order, players may
exile (face down) some or all of the cards in their hand.
Each player then draws one less card from their deck than the number they exiled.
Players who exiled at least one card may return to step 1 and repeat the process, drawing one less card each time.
Players shuffle all exiled cards into their deck.
The banned list can be found here http://edh.truespace.ca/EDH_Forum/viewtopic.php?t=261
Got this from from https://www.mtgsalvation.com/forums/the-game/commander-edh/196120-edh-rules-and-faq