Wellwisher

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

Immaculate Magistrate

{T}: Put a +1/+1 counter on target creature for each Elf you control.

Elvish Promenade

Create a 1/1 green Elf Warrior creature token for each Elf you control.

Heedless One

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

Nissa's Chosen

If Nissa's Chosen would die, put it on the bottom of its owner's library instead.

Priest of Titania

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

Timberwatch Elf

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

Harmonize

Nissa Revane

+1: Search your library for a card named Nissa's Chosen, put it onto the battlefield, then shuffle.
+1: You gain 2 life for each Elf you control.
−7: Search your library for any number of Elf creature cards, put them onto the battlefield, then shuffle.

Joraga Treespeaker

Level up {1}{G} ({1}{G}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 1-4
1/2
{T}: Add {G}{G}.
LEVEL 5+
1/4
Elves you control have "{T}: Add {G}{G}."

Elvish Archdruid

Other Elf creatures you control get +1/+1.
{T}: Add {G} for each Elf you control.

Wirewood Channeler

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

Imperious Perfect

Other Elves you control get +1/+1.
{G}, {T}: Create a 1/1 green Elf Warrior creature token.

Drove of Elves

Hexproof
Drove of Elves's power and toughness are each equal to the number of green permanents you control.

Forest

Jagged-Scar Archers

Jagged-Scar Archers's power and toughness are each equal to the number of Elves you control.
{T}: Jagged-Scar Archers deals damage equal to its power to target creature with flying.

Joraga Warcaller

Multikicker {1}{G} (You may pay an additional {1}{G} any number of times as you cast this spell.)
Joraga Warcaller enters the battlefield with a +1/+1 counter on it for each time it was kicked.
Other Elf creatures you control get +1/+1 for each +1/+1 counter on Joraga Warcaller.

Lys Alana Huntmaster

Whenever you cast an Elf spell, you may create a 1/1 green Elf Warrior creature token.