As I continue with my guild rebuilds after the black-green Tulgri Hosts (having, coincidentally, avoided doing anything containing blue thus far), I'll introduce this one as I have the others:
Ravnica is an immensely well-regarded plane, and most of its fans love it because of the guild system, allowing each of the ten two-color combinations to get relatively equal representation, its own identity, and a new keyword. And the ten guilds do capture the essence of what their colors are about, philosophically and mechanically - or at least part of it. Individual colors are deep enough that their philosophical essences can't be pinned down in one word, of course, and so are the intersections of two colors. And it becomes problematic when players think that all two-color cards, concepts, or factions need to fall in line with the appropriate Ravnica guild's beliefs.
So, as a thought experiment, and partly as speculation for the future of multicolor sets and perhaps even Ravnica itself, I will propose versions of Ravnica guilds that might have existed if R&D had chosen to focus on different aspects of the colors that make them up.
Switching back from enemy to allied colors for now, let me turn my attention to the interactions of black and red.
It's pretty easy to find flavor and mechanical overlap in black and red, the color combination of the chaotic evil alignment. Black's uncaring selfishness and red's emotional recklessness bring out the worst in each other, and these colors tend to get mechanics so similar that there has been a concerted effort to separate them, starting with black getting more defensive than its traditional suicide all-out attack strategy. After all, there's not a huge amount of difference between dealing N damage to a creature and giving it -N/-N, or "attacks each turn if able" and "can't block." These two colors have also historically notably had small creatures that came with drawbacks most often.
Now, as staunch of a Boros supporter as I am, I have a shameful secret with regard to Ravnica: I think the Rakdos guild is actually well-designed. I love hellbent, as a Johnny-ish mechanic that's really not encouraging you to do anything that outlandish (aggro decks would like to have empty hands because that means lots of stuff on the board), and even unleash, simple as it is, leads to some very interesting combat. The problem is largely one of flavor. It's not that there are not a lot of cool things to do with the Cult of Rakdos, it's that there are and they're not cohesive. It's not entirely clear what the Rakdos' purpose in Ravnica is - why where they allowed a guild charter in the Guildpact? Are they entertainers? Purveyors of luxury goods? Persons of easy virtue? The official thugs on retainer? What did Rakdos even say to convince the other nine paruns to essentially grant him a license to murder as he pleased as long as the rest of his activities were for the good of the city and the plane. Return to Ravnica's Rakdos were more consistently a kind of "twisted circus" of performers, but even that still seems like a meager reason to allow a psychopathic cult to run riot.
So I like the "indulgence" aspects of the Rakdos, but I'm unconvinced by the violence - turning up the former knob and the latter down led me to design the Yareele Gourmets.
"Good taste to the people!" is the motto of the Yareele - the ultimate exponents of art for profit. Chartered by an ancient, powerful, but lazy and titanically indulgent Vampire, Yardoth, the Yareele Gourmets are the purveyors of every kind of sensory experience, especially the gustatory. They cater the banquets of all the other guilds, and their kitchens are open to all from millionaires to beggars, because if there's something the Yareele love more than good food and drink, it's gold.
The Gourmets have a reputation of pouring their very heart and soul into their work, sometimes to an obsessive degree. They're willing and able to go through anything to get the finest ingredients; their culinary training makes them more than capable alchemists, apothecaries, and poisoners; and although they prefer to think of themselves as lovers rather than fighters their kitchen implements are definitely sharp enough to pierce flesh and bone.
My pleasure. My reaping. My guild.
Ability word - Savored - When you sacrifice this permanent, [effect].
Goblin Kitchen Boy R
Creature - Goblin (Common)
When Goblin Kitchen Boy enters the battlefield, it deals 1 damage to target player.
Savored - When you sacrifice Goblin Kitchen Boy, it deals 2 damage to each player.
"Hot sauce? I thought you said hot stones!"
Recipe for Disaster 1BR
As an additional cost to cast Recipe for Disaster, reveal a card at random from your hand.
Choose one - Return target card with the same converted mana cost as the revealed card from your graveyard to your hand; or each player loses life equal to the revealed card's converted mana cost.
Master of the Scullery 3BB
Creature - Vampire (Rare)
First strike, lifelink
Savored - When you sacrifice Master of the Scullery, you may pay any amount of life. If you do, draw that many cards.