Heedless One

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

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Rofellos, Llanowar Emissary

{T}: Add {G} for each Forest you control.

Elvish Archers

Forest

Island

Giant Growth

Target creature gets +3/+3 until end of turn.

Priest of Titania

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

Overrun

Creatures you control get +3/+3 and gain trample until end of turn. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)

Force Spike

Counter target spell unless its controller pays {1}.

Winter Orb

As long as this artifact is untapped, players can't untap more than one land during their untap steps.

Eladamri, Lord of Leaves

Other Elf creatures have forestwalk. (They can't be blocked as long as defending player controls a Forest.)
Other Elves have shroud. (They can't be the targets of spells or abilities.)

Quirion Ranger

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

Counterspell

Quirion Elves

As this creature enters, choose a color.
{T}: Add {G}.
{T}: Add one mana of the chosen color.

Elvish Champion

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