Decide on a deck type. Red decks have mostly spell effects used to deal damage to a player or his creatures, as such are fairly effective against elf decks. Other options are black decks that focus on destroying enemy creatures or anti-green cards.
An elven deck, in the card game "Magic: The Gathering," is a deck type in which the player uses mostly elf cards. Elf cards are all green creature cards which typically have a special tap effects. This makes elf decks difficult to combat as the player can summon large numbers of elf creatures. Defeating an elven deck will depending on several factors, such as your deck type and play style.
Fill your deck with cards that prevent creatures from attacking, such as Caltrops. This will help prevent early game attacks from your opponent's weaker creatures.
Play spell cards that prevent high damage creatures from attacking, such as Ensnaring Bridge. Many elven decks have cards that increase an elf card's damage based on the number of total elf cards in play.
Stack your deck with anti-green or flying creatures. These creatures cannot be blocked by green elf cards. Some elf cards are considered flying, so stacking your deck with flying creatures will also add to your defense.
Place creature destruction spell cards in your deck to remove some of your opponent's creatures from the game.