msem-instigator

{T}, Sacrifice Hazy Lagoon: Search your library for a Plains or Island card and put it onto the battlefield tapped, then shuffle.

({T}: Add {U} or {B}.)
Hazy Moorland enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Hazy Summits enters tapped.
{T}: Add {R} or {W}.
{1}, {T}: Add one mana of any color.

When Healing Center enters, you gain 2 life.
{T}: Add {C}.

{T}: Add {C}.
Wanderlust — {T}: Add one mana of any color. Activate only if you control four or more differently named lands. If you control seven or more, you may add three mana of that color instead.

({T}: Add {G} or {W}.)
Heart of the Glade enters tapped unless you control a basic Forest or a basic Plains.

Flying, vigilance, deathtouch, lifelink

Enchant creature
When Heartstrings leaves the battlefield, exile enchanted creature.
Whenever enchanted creature attacks or blocks, exile it at end of combat.

{T}: Add {C}.
When Heavenly Temple enters, target creature gains flying until end of turn.
{2}: Return Heavenly Temple from the battlefield to its owner's hand.

{T}, Pay 1 life: Add {U} or {R}.
{1}, {T}, Sacrifice Heist Headquarters: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Hellfire Caverns enters tapped.
{T}: Add {R}.
{2}{R}: Until end of turn, Hellfire Caverns becomes a 3/3 Devil creature with menace. Activate only if you're horrific.

{T}: Add {C}.
{T}, Reappropriate: Add {B} or {R}. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)

(Transform this if it's not attached to a creature. Pay {B} as a sorcery to unattach it.)
Enchant creature you control
Herald of Death's rider gets +1/+1.
Sacrifice a creature: Herald of Death's rider gets +2/+2 until end of turn.

(Transform this if it's not attached to a creature. Pay {4}{G} as a sorcery to unattach it.)
Enchant creature you control
Herdstrider's rider gets +1/+1 for each land you control and has trample.
Whenever Herdstrider's rider attacks, create an X/X green Elephant creature token with trample that's tapped and attacking, where X is that creature's power. Exile that token at the end of combat.

Heretic's Home enters tapped.
{T}: Add {R} or {G}.
When Heretic's Home enters, you may put a loyalty counter on a planeswalker you control.

Hibernation Den enters tapped.
{T}: Add {W}.
{W}, {T}: You gain 1 life. Activate only as a sorcery and only if you control a white creature.

{T}, Sacrifice Hidden Garden Entrance: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Monument {W}{U}{B}{R}{G} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

{T}, Pay 1 life: Add {G} or {U}.
{1}, {T}, Sacrifice Hidden Hollow: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

({T}: Add {R}.)
As Highland Dunes enters, you may pay 1 life. If you don't, Highland Dunes enters tapped.

({T}: Add {R} or {G}.)
Highland Vale enters tapped.

Highpoint Shrine enters tapped unless you played it from exile.
{T}: Add {W} or {U}.

Whenever a creature you control dies, put a soul counter on Hill of Souls.
{T}: Add {C}.
{T}, Remove a soul counter from Hill of Souls: Add one mana of any color.

Hiroto's Refuge enters tapped.
When Hiroto's Refuge enters, you may mill two cards.
{T}: Add {G} or {W}.

{T}: Add {C}.
{1}: Hoof Cliff Horngrove becomes a 2/2 Elemental creature until end of turn. It's still a land.
Menagerie — Whenever Hoof Cliff Horngrove becomes a creature, it gains your choice of +1/+1, flying, first strike, lifelink, trample, or haste until end of turn. This ability triggers only if there are five or more creature types among creatures you control.

When you attain Hopeless Lanonshee, create two 1/1 black Construct artifact creature tokens.
Whenever a creature dies, each opponent loses 1 life and you gain 1 life.