Play with the top card of your library revealed.
You may play lands and cast spells from the top of your library.

When Merfolk Observer enters the battlefield, look at the top card of target player's library.

Shuffle your library. Then exile the top card of your library. Until end of turn, you may play that card without paying its mana cost. (If it has X in its mana cost, X is 0.)
Storm (When you cast this spell, copy it for each spell cast before it this turn.)

When Nulltread Gargantuan enters the battlefield, put a creature you control on top of its owner's library.

Whenever an opponent shuffles their library, you may look at the top two cards of that library. You may exile one of those cards. Then put the rest on top of that library in any order.

Salvage Slasher gets +1/+0 for each artifact card in your graveyard.

You may sacrifice three artifacts rather than pay this spell's mana cost.
Exile three artifact cards from your graveyard: Return Salvage Titan from your graveyard to your hand.

Defender
Plainscycling , islandcycling (, Discard this card: Search your library for a Plains or Island card, reveal it, put it into your hand, then shuffle your library.)

As long as you control a Plains, Sejiri Merfolk has first strike and lifelink. (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Sejiri Steppe enters the battlefield tapped.
When Sejiri Steppe enters the battlefield, target creature you control gains protection from the color of your choice until end of turn.
: Add .

Landfall — Whenever a land enters the battlefield under your control, you may put a quest counter on Soul Stair Expedition.
Remove three quest counters from Soul Stair Expedition and sacrifice it: Return up to two target creature cards from your graveyard to your hand.

Target opponent exiles cards from the top of their library until they exile a nonland card. Until end of turn, you may cast that card without paying its mana cost.

[+1]: Untap up to two target artifacts.
[−X]: Search your library for an artifact card with converted mana cost X or less and put it onto the battlefield. Then shuffle your library.
[−5]: Artifacts you control become artifact creatures with base power and toughness 5/5 until end of turn.

Draw a card.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Draw three cards. Then discard two cards unless you discard an artifact card.

Choose one —
• Thunderbolt deals 3 damage to target player or planeswalker.
• Thunderbolt deals 4 damage to target creature with flying.

As an additional cost to cast this spell, sacrifice a creature.
Draw three cards.