The Lost Caverns of Ixalan

Warden of the Inner Sky | Creature | Human Soldier | As long as Warden of the Inner Sky has three or more counters on it, it has flying and vigilance. Tap three untapped artifacts and/or creatures you control: Put a +1/+1 counter on Warden of the Inner Sky. Scry 1. Activate only as a sorcery. | Raoul Vitale

Stalactite Stalker | Creature | Goblin Rogue | Menace At the beginning of your end step, if you descended this turn, put a +1/+1 counter on Stalactite Stalker. {2}{B}, Sacrifice Stalactite Stalker: Target creature gets -X/-X until end of turn, where X is Stalactite Stalker's power. | Olivier Bernard

Jadelight Spelunker | Creature | Merfolk Scout | When Jadelight Spelunker enters the battlefield, it explores X times. (To have it explore, 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 that creature, then put the card back or put it into your graveyard.) | Izzy