Flying
When Hoarding Rocs enters, look at the top three cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom in a random order.

Hold to the Flame enters with a blaze counter on it.
Whenever you cast an instant or sorcery spell with mana value 4 or greater, put a blaze counter on Hold to the Flame. Then it deals damage equal to the number of blaze counters on it to any target.

Flash
Enchant creature
Enchanted creature can't attack or block.

Holo-Map enters with two charge counters on it.
{1}, {T}, Remove a charge counter from Holo-Map: Target creature can't be blocked this turn. Scry 2.

Ward {3}
Whenever Horror of the Mystic Sea attacks, defending player mills two cards. If they milled two nonland cards this way, Horror of the Mystic Sea can't be blocked this turn.

Ward—Sacrifice a permanent.
Whenever Host of the Neverending Revel enters or attacks, each player sacrifices a nonland, nontoken permanent. For each player who doesn't, you draw a card.

When Humble Barkeep enters, create a Food token.
Whenever you sacrifice a Food, put a +1/+1 counter on Humble Barkeep.

Hundred-Handed Pillars enters tapped.
{T}: Add {W} or {U}.
{7}{W/U}: Hundred-Handed Pillars becomes a 4/6 white and blue Giant creature with vigilance until end of turn. It's still a land. This ability costs {X} less to activate, where X is your devotion to white and blue. Activate only once each turn.

Trample
When Hunger's Door enters, you may return target Aura card from your graveyard to the battlefield attached to Hunger's Door.

Hyperloop Obelisk enters tapped.
{T}: Add {U}, {B}, or {R}.
{VP}{VP}{VP}{VP}, Discard Hyperloop Obelisk: Untap target creature. It gets +4/+4 until end of turn.

Favored
Whenever Iara, Blessed-Hart attacks, Iara and another target attacking creature gain double strike until end of turn.

{VP}{VP}{VP}: Reveal the top seven cards of your library. You may have Iconic Hologram become a copy of a legendary creature card revealed this way until end of turn. Put the revealed cards on the bottom of your library in a random order.

Trample
When Idealistic Voter enters, make a pledge.

{X}, {T}, Sacrifice another creature: Create a token that's a copy of target nontoken creature you control other than Identity Forger with mana value X.

Menace
Whenever Ignited Soul deals combat damage to a player, you may discard a card. If you do, draw a card.

When you cast this spell, target player skips their next combat phase.
[+1]: Create a 3/1 white Knight creature token with “As long as it's your turn, this creature has indestructible.”
[0]: Exile a permanent card from your graveyard. Return that card to the battlefield at the beginning of your next turn's end step.
[–3]: At the beginning of your next turn's end step, destroy all creatures.

Enchant land
Enchanted land is a 4/4 Dryad creature with reach, vigilance, and haste. It's still a land.
When enchanted land dies, return it to its owner's hand.

Trample
When Imperfect Fugisaur enters, you may sacrifice an artifact. If you do, it gains haste until end of turn.
Whenever Imperfect Fugisaur deals combat damage to a player, that player sacrifices an artifact. If they can't, you draw a card.

Trample, haste
When Impetuous Knight enters, target opponent creates a Windmill artifact token with “{T}: Prevent all combat damage target Knight would deal to you this turn”.
Impetuous Knight attacks each combat if able as long as an opponent controls a Windmill.

Whenever Implacable Shrine-Guard attacks, for each color, do the following if your devotion to that color is three or greater.
{W} — Create a 1/1 white Human creature token.
{U} — Draw a card.
{B} — Each opponent loses 2 life.
{R} — Create a Treasure token.
{G} — You gain 3 life.

Imposing Oddity enters with X +1/+1 counters on it.
Whenever Imposing Oddity becomes spellcharged, put a +1/+1 counter on it.
Spellcharge 4
When Imposing Oddity dies, you may put its counters on another target Ruin you control.

Ward {2}
Imposing Serpent enters with X +1/+1 counters on it.

When Indentured Labourer enters, you draw a card and lose 1 life.

Vigilance
When Indomitable Jicru enters, you gain 5 life and draw a card. If it wandered, creatures you control get +2/+2 until end of turn.
Wander {6}{G}{W}

Whenever you attack, double target attacking creature's power and toughness until end of turn.