Overrun

Creatures you control get +3/+3 and gain trample until end of turn.

Elvish Warmaster

Whenever one or more other Elves you control enter, create a 1/1 green Elf Warrior creature token. This ability triggers only once each turn.
{5}{G}{G}: Elves you control get +2/+2 and gain deathtouch until end of turn.

Greenweaver Druid

Elven Ambush

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

Marwyn, the Nurturer

Whenever another Elf you control enters, put a +1/+1 counter on Marwyn, the Nurturer.
{T}: Add an amount of {G} equal to Marwyn's power.

Elvish Archdruid

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

Wildwood Scourge

Wildwood Scourge enters with X +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another non-Hydra creature you control, put a +1/+1 counter on Wildwood Scourge.

Dwynen's Elite

When Dwynen's Elite enters, if you control another Elf, create a 1/1 green Elf Warrior creature token.

Voracious Hydra

Trample
Voracious Hydra enters with X +1/+1 counters on it.
When Voracious Hydra enters, choose one —
• Double the number of +1/+1 counters on Voracious Hydra.
• Voracious Hydra fights target creature you don't control.

Ezuri, Renegade Leader

{G}: Regenerate another target Elf.
{2}{G}{G}{G}: Elf creatures you control get +3/+3 and gain trample until end of turn.

Forest

Tajuru Blightblade

Imperious Perfect

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

Ashaya, Soul of the Wild

Ashaya, Soul of the Wild's power and toughness are each equal to the number of lands you control.
Nontoken creatures you control are Forest lands in addition to their other types. (They're still affected by summoning sickness.)

Canopy Tactician

Other Elves you control get +1/+1.
{T}: Add {G}{G}{G}.

Immaculate Magistrate

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

Lys Alana Bowmaster

Reach
Whenever you cast an Elf spell, you may have Lys Alana Bowmaster deal 2 damage to target creature with flying.