Wirewood Hivemaster

Whenever another nontoken Elf enters, you may create a 1/1 green Insect creature token.

Elvish Vanguard

Whenever another Elf enters, put a +1/+1 counter on Elvish Vanguard.

Elvish Scrapper

{G}, {T}, Sacrifice Elvish Scrapper: Destroy target artifact.

Wirewood Herald

When Wirewood Herald dies, you may search your library for an Elf card, reveal that card, put it into your hand, then shuffle.

Wellwisher

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

Forest

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When Rancor is put into a graveyard from the battlefield, return Rancor to its owner's hand.

Timberwatch Elf

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

Wirewood Symbiote

Return an Elf you control to its owner's hand: Untap target creature. Activate only once each turn.

Elvish Champion

Other Elf creatures get +1/+1 and have forestwalk. (They can't be blocked as long as defending player controls a Forest.)

Ambush Commander

Forests you control are 1/1 green Elf creatures that are still lands.
{1}{G}, Sacrifice an Elf: Target creature gets +3/+3 until end of turn.

Heedless One

Trample
Heedless One's power and toughness are each equal to the number of Elves on the battlefield.

Priest of Titania

{T}: Add {G} for each Elf on the battlefield.

Llanowar Elves

Wirewood Channeler

{T}: Add X mana of any one color, where X is the number of Elves on the battlefield.

Taunting Elf

All creatures able to block Taunting Elf do so.

Wirewood Pride

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