Guilds

The Guilds are ten factions on the city plane of Ravnica. Each Guild is linked to a certain color pair. In paper Magic: The Gathering the Guilds exist since the original Ravnica set (2005). In Magic: The Gathering Arena the Guilds were firstly featured with Guilds of Ravnica.

Details
Apart from the vast lore the single names for each Guild are often used to describe the color combination of a dual-colored deck. For example, if somebody talks about a "Dimir" deck, the deck is blue-black.