Wellwisher

{T}: You gain 1 life for each Elf on the battlefield.

Tainted Wood

{T}: Add {C}.
{T}: Add {B} or {G}. Activate only if you control a Swamp.

Prowess of the Fair

Whenever another nontoken Elf is put into your graveyard from the battlefield, you may create a 1/1 green Elf Warrior creature token.

Blade of the Bloodchief

Whenever a creature dies, put a +1/+1 counter on equipped creature. If equipped creature is a Vampire, put two +1/+1 counters on it instead.
Equip {1}

Scarred Vinebreeder

{2}{B}, Exile an Elf card from your graveyard: Scarred Vinebreeder gets +3/+3 until end of turn.

Llanowar Elves

Fallen Ideal

Enchant creature
Enchanted creature has flying and "Sacrifice a creature: This creature gets +2/+1 until end of turn."
When Fallen Ideal is put into a graveyard from the battlefield, return Fallen Ideal to its owner's hand.

Golgari Rot Farm

Golgari Rot Farm enters tapped.
When Golgari Rot Farm enters, return a land you control to its owner's hand.
{T}: Add {B}{G}.

Moonglove Winnower

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Swamp

Sadistic Glee

Enchant creature
Whenever a creature dies, put a +1/+1 counter on enchanted creature.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature.

Elvish Visionary

When Elvish Visionary enters, draw a card.

Bloodthrone Vampire

Sacrifice a creature: Bloodthrone Vampire gets +2/+2 until end of turn.

Timberwatch Elf

{T}: Target creature gets +X/+X until end of turn, where X is the number of Elves on the battlefield.