As Molten Echoes enters the battlefield, choose a creature type.
Whenever a nontoken creature of the chosen type enters the battlefield under your control, create a token that's a copy of that creature. That token gains haste. Exile it at the beginning of the next end step.

Constellation — Whenever Nylea's Colossus or another enchantment enters the battlefield under your control, double target creature's power and toughness until end of turn.

Constellation — Whenever Oakheart Dryads or another enchantment enters the battlefield under your control, target creature gets +1/+1 until end of turn.

When Oath of Kaya enters the battlefield, it deals 3 damage to any target and you gain 3 life.
Whenever an opponent attacks a planeswalker you control with one or more creatures, Oath of Kaya deals 2 damage to that player and you gain 2 life.

Whenever Oath of the Ancient Wood or another enchantment enters the battlefield under your control, you may put a +1/+1 counter on target creature.

As Outpost Siege enters the battlefield, choose Khans or Dragons.
• Khans — At the beginning of your upkeep, exile the top card of your library. Until end of turn, you may play that card.
• Dragons — Whenever a creature you control leaves the battlefield, Outpost Siege deals 1 damage to any target.

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.

Whenever a creature enters the battlefield under your control, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)

When Path of Mettle enters the battlefield, it deals 1 damage to each creature that doesn't have first strike, double strike, vigilance, or haste.
Whenever you attack with at least two creatures that have first strike, double strike, vigilance, and/or haste, transform Path of Mettle.

Whenever you cast a creature spell, create a 3/3 green Beast creature token.
Whenever you cast a noncreature spell, put three +1/+1 counters on target creature you control.
Whenever a land enters the battlefield under your control, you gain 3 life.

Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.
Whenever a creature enters the battlefield under an opponent's control, you may attach Prison Term to that creature.

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature enters the battlefield under your control, Purphoros deals 2 damage to each opponent.
: Creatures you control get +1/+0 until end of turn.

Whenever a Goblin enters the battlefield under your control, you may put a quest counter on Quest for the Goblin Lord.
As long as Quest for the Goblin Lord has five or more quest counters on it, creatures you control get +2/+0.

Landfall — Whenever a land enters the battlefield under your control, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Create a 1/1 white Kor Ally creature token.
• Creatures you control get +1/+1 until end of turn.

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Target creature gets +1/+0 and gains deathtouch until end of turn.
• Each opponent loses 1 life and you gain 1 life.

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Put a +1/+1 counter on target creature.
• You gain 2 life.

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Target creature gets +2/+0 until end of turn.
• Target creature can't block this turn.

Kicker (You may pay an additional as you cast this spell.)
When Roost of Drakes enters the battlefield, if it was kicked, create a 2/2 blue Drake creature token with flying.
Whenever you cast a kicked spell, create a 2/2 blue Drake creature token with flying.

Whenever a creature enters the battlefield under your control, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)
Whenever you cast a spell that targets a creature you control, draw a card.