You may cast Harbinger of the Tides as though it had flash if you pay more to cast it. (You may cast it any time you could cast an instant.)

When Harbinger of the Tides enters the battlefield, you may return target tapped creature an opponent controls to its owner's hand.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Harbor Serpent can't attack unless there are five or more Islands on the battlefield.

Flying

When Harrier Strix enters the battlefield, tap target permanent.

: Draw a card, then discard a card.

Creatures your opponents control get -1/-0.

Vigilance

Haunting Figment can't be blocked as long as you've cast an instant or sorcery spell this turn.

, , Exile a creature card from your graveyard: Create a 2/2 black Zombie creature token, then put a +1/+1 counter on each Zombie creature you control.

Flying, protection from red

As an additional cost to cast this spell, exile a creature card from your graveyard.

Headless Skaab enters the battlefield tapped.

Landfall — Whenever a land enters the battlefield under your control, target player mills three cards.

Whenever you cycle or discard a card, Hekma Sentinels gets +1/+1 until end of turn.

Graft 3 (This creature enters the battlefield with three +1/+1 counters on it. Whenever another creature enters the battlefield, you may move a +1/+1 counter from this creature onto it.)

: Target creature with a +1/+1 counter on it gains flying until end of turn.

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)

Other Knights you control have horsemanship.

Creatures you control with +1/+1 counters on them can't be blocked.

Vigilance

: Hermitic Nautilus gets +3/-3 until end of turn.

Flying

When Hidetsugu and Kairi enters the battlefield, draw three cards, then put two cards from your hand on top of your library in any order.

When Hidetsugu and Kairi dies, exile the top card of your library. Target opponent loses life equal to its mana value. If it's an instant or sorcery card, you may cast it without paying its mana cost.

Ninjutsu (, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)

Whenever Higure, the Still Wind deals combat damage to a player, you may search your library for a Ninja card, reveal it, put it into your hand, then shuffle.

: Target Ninja creature can't be blocked this turn.

Flying

Hinterland Drake can't block artifact creatures.

You may choose not to untap Hisoka's Guard during your untap step.

, : Target creature you control other than Hisoka's Guard has shroud for as long as Hisoka's Guard remains tapped. (It can't be the target of spells or abilities.)

, Exile Holographic Double from your hand: Choose a creature card in your hand. Conjure a duplicate of it into your hand.

When Homarid Explorer enters the battlefield, target player mills four cards.

: Homarid Warrior gains shroud until end of turn and doesn't untap during your next untap step. Tap Homarid Warrior. (A creature with shroud can't be the target of spells or abilities.)

Vigilance, trample, haste

: You may play target Elemental card from your graveyard without paying its mana cost.

Flash

Flying, trample

Whenever you draw a card, you gain 1 life.

Flying

When Horizon Scholar enters the battlefield, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

When Hostage Taker enters the battlefield, exile another target creature or artifact until Hostage Taker leaves the battlefield. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

, : Target creature doesn't untap during its controller's next untap step.

, : 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.)

Flying

Hoverguard Observer can block only creatures with flying.

Flash

If an opponent would draw a card except the first one they draw in each of their draw steps, instead you create a Treasure token. (It's an artifact with ", Sacrifice this artifact: Add one mana of any color.")

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Hunted Phantasm can't be blocked.

When Hunted Phantasm enters the battlefield, target opponent creates five 1/1 red Goblin creature tokens.

At the beginning of your end step, if you've cast a noncreature spell this turn, reveal the top five cards of your library. For each card type among noncreature spells you've cast this turn, you may put a card of that type from among the revealed cards into your hand. Put the rest on the bottom of your library in a random order.

When you cast this spell, you gain half X life and draw half X cards. Round down each time.

Flying, trample

Hydroid Krasis enters the battlefield with X +1/+1 counters on it.

Flying

, Sacrifice Hydromorph Gull: Counter target spell that targets a creature you control.

Flying, haste

You may cast sorcery spells as though they had flash. (You may cast them any time you could cast an instant.)

Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)

Flying

You control enchanted creature.

Enchanted creature gets +1/+1 and has flying.

Whenever a player draws their second card each turn, that player exiles the top card of their library.

During each player's turn, that player may cast a spell from among the cards they don't own exiled with Ian Malcolm, Chaotician, and mana of any type can be spent to cast it.

Whenever Iceberg Titan attacks, you may tap or untap target artifact or creature.

Flying

When Icefall Regent enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Icefall Regent.

Spells your opponents cast that target Icefall Regent cost more to cast.

Flying

Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)

When Icefeather Aven is turned face up, you may return another target creature to its owner's hand.

Whenever you cast a noncreature spell, put an oil counter on Ichor Synthesizer.

As long as Ichor Synthesizer has four or more oil counters on it, it gets +2/+0 and can't be blocked.

Vanishing 3

Imprint — When Idris, Soul of the TARDIS enters the battlefield, exile another artifact you control until Idris leaves the battlefield.

Idris has all activated and triggered abilities of the exiled card and gets +X/+X, where X is the exiled card's mana value.

Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)

Flying, trample

Whenever this creature mutates, exile cards from the top of your library until you exile a nonland permanent card. Put that card onto the battlefield or into your hand.

Draft Illusionary Informant face up.

During the draft, you may turn Illusionary Informant face down. If you do, look at the next card drafted by a player of your choice.

Flying

Flying

When Illusionary Servant becomes the target of a spell or ability, sacrifice it.

Flash (You may cast this spell any time you could cast an instant.)

Whenever Illusory Ambusher is dealt damage, draw that many cards.

Flying

When you cast a spell, sacrifice Illusory Demon.

At the beginning of your upkeep, if you have a card in hand, return Imaginary Pet to its owner's hand.

Ward (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays .)

At the beginning of your end step, if you have the initiative, draw a card. Draw another card if you've completed a dungeon.

Choose a Background (You can have a Background as a second commander.)

Flying

Whenever Impaler Shrike deals combat damage to a player, you may sacrifice it. If you do, draw three cards.