Ixalan

Dreamcaller Siren | Creature | Siren Pirate | Flash Flying Dreamcaller Siren can block only creatures with flying. When Dreamcaller Siren enters the battlefield, if you control another Pirate, tap up to two target nonland permanents. | Eric Deschamps

Herald of Secret Streams | Creature | Merfolk Warrior | Creatures you control with +1/+1 counters on them can't be blocked. | Sara Winters

Sanctum Seeker | Creature | Vampire Knight | Whenever a Vampire you control attacks, each opponent loses 1 life and you gain 1 life. | Volkan Baǵa

Captivating Crew | Creature | Human Pirate | {3}{R}: Gain control of target creature an opponent controls until end of turn. Untap that creature. It gains haste until end of turn. Activate only as a sorcery. | Winona Nelson

Emperor's Vanguard | Creature | Human Scout | Whenever Emperor's Vanguard deals combat damage to a player, 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 this creature, then put the card back or put it into your graveyard.) | Victor Adame Minguez

Ripjaw Raptor | Creature | Dinosaur | Enrage — Whenever Ripjaw Raptor is dealt damage, draw a card. | Ryan Pancoast

Waker of the Wilds | Creature | Merfolk Shaman | {X}{G}{G}: Put X +1/+1 counters on target land you control. That land becomes a 0/0 Elemental creature with haste. It's still a land. | Shreya Shetty

Hostage Taker | Creature | Human Pirate | 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 you may spend mana as though it were mana of any type to cast that spell. | Wayne Reynolds