Three Blind Mice

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I — Create a 1/1 white Mouse creature token.
II, III — Create a token that's a copy of target token you control.
IV — Creatures you control get +1/+1 and gain vigilance until end of turn.

Song of the Worldsoul

Whenever you cast a spell, populate. (Create a token that's a copy of a creature token you control.)

Garden of Freyalise

As Garden of Freyalise enters the battlefield, you may pay 3 life. If you don't, it enters the battlefield tapped.
{T}: Add {G}.

Disciple of Freyalise

When Disciple of Freyalise enters the battlefield, you may sacrifice another creature. If you do, you gain X life and draw X cards, where X is that creature's power.

Disciple of Freyalise // Garden of Freyalise

Pandemonium

Whenever a creature enters the battlefield, that creature's controller may have it deal damage equal to its power to any target of their choice.

Where Ancients Tread

Whenever a creature with power 5 or greater enters the battlefield under your control, you may have Where Ancients Tread deal 5 damage to any target.

Ghired, Conclave Exile

When Ghired, Conclave Exile enters the battlefield, create a 4/4 green Rhino creature token with trample.
Whenever Ghired attacks, populate. The token enters the battlefield tapped and attacking. (To populate, create a token that's a copy of a creature token you control.)

Terror of the Peaks

Flying
Spells your opponents cast that target Terror of the Peaks cost an additional 3 life to cast.
Whenever another creature enters the battlefield under your control, Terror of the Peaks deals damage equal to that creature's power to any target.

Ezuri's Predation

For each creature your opponents control, create a 4/4 green Phyrexian Beast creature token. Each of those tokens fights a different one of those creatures.

Scourge of Valkas

Flying
Whenever Scourge of Valkas or another Dragon enters the battlefield under your control, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn.

Saproling Burst

Fading 7 (This enchantment enters the battlefield with seven fade counters on it. At the beginning of your upkeep, remove a fade counter from it. If you can't, sacrifice it.)
Remove a fade counter from Saproling Burst: Create a green Saproling creature token. It has "This creature's power and toughness are each equal to the number of fade counters on Saproling Burst."
When Saproling Burst leaves the battlefield, destroy all tokens created with Saproling Burst. They can't be regenerated.

Warstorm Surge

Whenever a creature enters the battlefield under your control, it deals damage equal to its power to any target.

Ghired, Mirror of the Wilds

Haste
Nontoken creatures you control have "{T}: Create a token that's a copy of target token you control that entered the battlefield this turn."