This spell can't be countered.
Trample
Hexproof from mana value 3 or less

For each card type, you may return a card of that type from your graveyard to your hand. Exile Witness the Ages.

Lifelink, haste
Other creatures you control have lifelink and haste.
Once each turn, when a creature you control dies during your turn, you may gain control of target creature an opponent controls until end of turn. Untap that creature.

Choose one —
• Target creature you control gets +2/+0 until end of turn. It deals damage equal to its power to up to one target creature or planeswalker.
• Return target nonland permanent card with mana value 3 or less from your graveyard to the battlefield tapped.
• Target player discards two cards.

This spell costs {1} less to cast for each Mantra card in your graveyard.
Menace
Whenever you cast a Mantra spell, you may put Atrah's Chantkeeper from your graveyard on top of your library.

{2}, {T}: Surveil 1.
{3}, {T}, Sacrifice Auroric Waygate: Return target card from your graveyard to your hand.

Flying
Awakened Guardian enters with a +1/+1 counter on it for each land card in your graveyard.

{3}, {T}, Sacrifice Bonewhisper Idol: It deals 3 damage to target creature.

{2}, {T}, Sacrifice Bottled Sunlight: Shuffle up to five other target cards from your graveyard into your library, then draw a card.

Master of Monument to the Thirty
{30}: Curator of Myth deals 30 damage to any target.

Equipped creature gets +2/+0.
Whenever equipped creature attacks, you may mill three cards. If a creature card was milled this way, create a 1/1 blue Spirit creature token with flying. If a land card was milled this way, you gain 3 life.
Equip {2}

Equipped creature gets +2/+0.
Whenever equipped creature attacks, surveil 1.
Equip {2}

Equipped creature gets +1/+0.
Whenever equipped creature attacks, you may untap target land.
Equip {1}

Monument to the Thirty enters tapped.
{T}: Add X mana of any one color, where X is the number of Monuments you control.
A deck can have up to thirty cards named Monument to the Thirty.

Defender
{1}, {T}: Add one mana of any color.

{2}, {T}: Exile the top card of your library face down and look at it.
When Qamutiik Snowrunner attacks, you may put a card exiled with it into your hand.
Crew 3

Once each turn, when a land card is put into your graveyard from anywhere other than the battlefield, you may put it onto the battlefield tapped.

If Witness to the First Word is in any zone, effects from spells and abilities you control count it as a Mantra.

Alruq Veil-Boundary enters tapped.
When Alruq Veil-Boundary enters, surveil 1.
{T}: Add {W}.

Bloodfell Caves enters tapped.
When Bloodfell Caves enters, you gain 1 life.
{T}: Add {B} or {R}.

Blossoming Sands enters tapped.
When Blossoming Sands enters, you gain 1 life.
{T}: Add {G} or {W}.

As Clearwater Grotto enters, you may pay 2 life. If you don't, it enters tapped.
{T}: Add {G} or {U}.

Dhagiri Veil-Boundary enters tapped.
When Dhagiri Veil-Boundary enters, surveil 1.
{T}: Add {U}.

Dismal Backwater enters tapped.
When Dismal Backwater enters, you gain 1 life.
{T}: Add {U} or {B}.

{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.