This is maybe one of the most fun decks I've played in standard... here's how it works:
Almost all the creatures have an ETB ability, which work well with Thassa, Deep-Dwelling and Teferi's Time Twist, including:
Ayara, First of Locthwain - makes it so every time something enters OR is flickered, they lose 1 and you gain 1
Blight-Breath Catoblepas - kind of expensive, but basically kills a creature every turn
Atris, Oracle of Half-Truths - bad fact or fiction, but for free every turn?
Cavalier of Night - kill their tough creatures with a flicker
Yarok's Fenlurker - if you're worried about their hand, this guy is deadly to flicker again and again
Gray Merchant of Asphodel - of course, this guy is incredible. You get the kill in only a couple turns!
Lost Legion - pick your best cards every turn
The non-ETB creatures are important too:
Erebos, Bleak-Hearted - this guy is big and indestructible, and almost always a creature. Why not?
Murderous Rider - helps with devotion, kills stuff
Tymaret, Chosen from Death - helps with devotion, keeps annoying cards out of graveyard
Thassa, Deep-Dwelling - last but not least, the bae of this deck, arguably the best card in standard, makes this deck better in every way.
