A list of cards can be found here, a card gallery will be available soon.
Guilds of Ravnica was added to MTG Arena as part of the September 27th 2018 open beta game update. The paper card set will be released on October 5, 2018.
Themes & Mechanics
The following mechanics were announced on August 30, 2018:
Convoke is a static keyword ability that lets you tap creatures rather than pay mana to cast a spell.
Convoke in Guilds of Ravnica is exclusive to the Selesnya guild.
When a creature with Mentor attacks, you put a +1/+1 counter on an attacking creature with less power.
Mentor is the mechanic linked to the Boros guild.
Surveil is like Scry, but instead of putting cards on the bottom of your library, they go to your graveyard.
Surveil is the mechanic linked to the Dimir guild.
You can play Instants and Sorceries with Jump-Start from your graveyard by discarding another card, paying mana and exiling the spell.
Jump-Start is the mechanic linked to the Izzet guild.
Undergrowth abilities care about the number of creatures in your graveyard.
Undergrowth is the mechanic linked to the Golgari guild.