Elvish Vanguard

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

Birchlore Rangers

Tap two untapped Elves you control: Add one mana of any color.
Morph {G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Forest

Timberwatch Elf

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

Lead the Stampede

Look at the top five cards of your library. You may reveal any number of creature cards from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in any order.

Quirion Ranger

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

Llanowar Elves

Strength in Numbers

Until end of turn, target creature gains trample and gets +X/+X, where X is the number of attacking creatures.