Have

High Perfect Morcant

Whenever High Perfect Morcant or another Elf you control enters, each opponent blights 1. (They each put a -1/-1 counter on a creature they control.)
Tap three untapped Elves you control: Proliferate. Activate only as a sorcery. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Getting

Morcant's Eyes

At the beginning of your upkeep, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{4}{G}{G}, Sacrifice this enchantment: Create X 2/2 black and green Elf creature tokens, where X is the number of Elf cards in your graveyard. Activate only as a sorcery.

Twilight Diviner

When this creature enters, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
Whenever one or more other creatures you control enter, if they entered or were cast from a graveyard, create a token that's a copy of one of them. This ability triggers only once each turn.

Swamp

Dawn-Blessed Pennant

As this artifact enters, choose Elemental, Elf, Faerie, Giant, Goblin, Kithkin, Merfolk, or Treefolk.
Whenever a permanent you control of the chosen type enters, you gain 1 life.
{2}, {T}, Sacrifice this artifact: Return target card of the chosen type from your graveyard to your hand.

Dawnhand Dissident

{T}, Blight 1: Surveil 1.
{T}, Blight 2: Exile target card from a graveyard.
During your turn, you may cast creature spells from among cards you own exiled with this creature by removing three counters from among creatures you control in addition to paying their other costs.

Moon-Vigil Adherents

Trample
This creature gets +1/+1 for each creature you control and each creature card in your graveyard.

Champions of the Perfect

As an additional cost to cast this spell, behold an Elf and exile it. (Exile an Elf you control or an Elf card from your hand.)
Whenever you cast a creature spell, draw a card.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Gloom Ripper

When this creature enters, target creature you control gets +X/+0 until end of turn and up to one target creature an opponent controls gets -0/-X until end of turn, where X is the number of Elves you control plus the number of Elf cards in your graveyard.

Llanowar Elves

Abomination of Llanowar

Vigilance; menace (This creature can't be blocked except by two or more creatures.)
Abomination of Llanowar's power and toughness are each equal to the number of Elves you control plus the number of Elf cards in your graveyard.

Trystan, Penitent Culler

Deathtouch
Whenever this creature transforms into Trystan, Penitent Culler, mill three cards, then you may exile an Elf card from your graveyard. If you do, each opponent loses 2 life.
At the beginning of your first main phase, you may pay {G}. If you do, transform Trystan.

Trystan, Callous Cultivator

Deathtouch
Whenever this creature enters or transforms into Trystan, Callous Cultivator, mill three cards. Then if there is an Elf card in your graveyard, you gain 2 life.
At the beginning of your first main phase, you may pay {B}. If you do, transform Trystan.

Trystan, Callous Cultivator // Trystan, Penitent Culler

Forest

Formidable Speaker

When this creature enters, you may discard a card. If you do, search your library for a creature card, reveal it, put it into your hand, then shuffle.
{1}, {T}: Untap another target permanent.

Eclipsed Elf

When this creature enters, look at the top four cards of your library. You may reveal an Elf, Swamp, or Forest card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Elvish Guidance

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G} for each Elf on the battlefield.

Scarblade's Malice

Target creature you control gains deathtouch and lifelink until end of turn. When that creature dies this turn, create a 2/2 black and green Elf creature token.

Lluwen, Imperfect Naturalist

When Lluwen enters, mill four cards, then you may put a creature or land card from among the milled cards on top of your library.
{2}{B/G}{B/G}{B/G}, {T}, Discard a land card: Create a 1/1 black and green Worm creature token for each land card in your graveyard.

Bloodline Bidding

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Choose a creature type. Return all creature cards of the chosen type from your graveyard to the battlefield.

Unbury

Choose one —
• Return target creature card from your graveyard to your hand.
• Return two target creature cards that share a creature type from your graveyard to your hand.

Trystan's Command

Choose two —
• Create a token that's a copy of target Elf you control.
• Return one or two target permanent cards from your graveyard to your hand.
• Destroy target creature or enchantment.
• Creatures target player controls get +3/+3 until end of turn. Untap them.

Gathering Stone

As this artifact enters, choose a creature type.
Spells you cast of the chosen type cost {1} less to cast.
When this artifact enters and at the beginning of your upkeep, look at the top card of your library. If it's a card of the chosen type, you may reveal it and put it into your hand. If you don't put the card into your hand, you may put it into your graveyard.

Eclipsed Realms

As this land enters, choose Elemental, Elf, Faerie, Giant, Goblin, Kithkin, Merfolk, or Treefolk.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a spell of the chosen type or activate an ability of a source of the chosen type.

Lathril, Blade of the Elves

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Lathril deals combat damage to a player, create that many 1/1 green Elf Warrior creature tokens.
{T}, Tap ten untapped Elves you control: Each opponent loses 10 life and you gain 10 life.

Witch's Cottage

({T}: Add {B}.)
This land enters tapped unless you control three or more other Swamps.
When this land enters untapped, you may put target creature card from your graveyard on top of your library.

Morcant's Loyalist

Other Elves you control get +1/+1.
When this creature dies, return another target Elf card from your graveyard to your hand.