There are neither traditional heroes nor villains in the grimdark. One-dimensional bad guys are boring in any genre. Forget one-dimensional good guys. No one buys pure heroes anymore, and the grimdark tends to chew honorable actors up and spit them out for their naivety.
Grimdark characters, like in real life, are shades of grey and often act for their own interests rather than serving a greater good. Also, if they serve an organization, ideal, or some higher authority, expect it to be greater, but not necessarily good. Here be fanatics, blind followers, and zealots.
Considering that most people act out of self-interest, who can you really trust? Is it as simple as whose interests align with yours? Usually, but let’s take a deeper dive into alliances in the grimdark.

Common Enemies
The enemy of my enemy is rumored to be my friend. A great way to ally an antihero with another character is to put them on the same side of the field, opposing a regime, person, or part of the social order. Even if these characters would never get along in a million years, pitting them against a common enemy is enough to have them set aside their petty differences and work together.
Speaking of, you know what a great way to get people to work together is? Make them hate a common enemy. On a small scale, this is used by drill instructors or perverse teachers to get their squad/students to work together as a team. On a more massive geopolitical scale, you have people committing all sorts of atrocities against an “other” that they’re all riled up to hate. We see this all through real life, not just in the grimdark. I don’t even have to invoke Godwin’s Law.
A mastermind doesn’t always have to pull the strings, but the manipulation is always fun to read. It’s also a fun twist when the people who are being played turn on the player, creating a “common enemy” situation where the manipulator gets hoisted. Always a good time.

Self-Serving Truces
What if someone was previously an enemy, but they have to work with you now? Well…why? What’s the reason for the truce? Could be common enemies as above, but it’s always called between the parties. If there are outside forces making them call a truce, it’s acknowledged by the parties burying the hatchet.
But is burying the hatchet really the start of a beautiful friendship? Or is it a means to an end? It can blossom into a sort-of friendship, like Arya Stark and Sandor Clegane in A Song of Ice and Fire. But this type of alliance can deteriorate quickly, especially if push comes to shove. Especially if you need to leave the other ally for dead so you won’t be eaten by wolves or killed by marauders.
What about love? Love and hate are, after all, opposite sides of the same coin. If two previous enemies have to call a truce, and there’s bounds for attraction, well, the hate to love thing is universal in literature. Lots of people swoon for the enemies-to-lovers trope. Will the happy couple live happily ever after? In the grimdark, you never know.
Especially considering the sociological themes. In grimdark, true love doesn’t conquer all just because. External circumstances, like birth station, cultural lenses, customs, and laws all influence the story just as much as dragons, magic, and gods do. These aren’t always obstacles that the hero can just overcome with pluck and luck. Like in our world, they just are, and no matter how much a stink you make, they’re still there.
That said, if characters have to make an alliance, and then return home to the social customs, norms, and laws that will keep them apart, do they break up, do they decide not to return, or do they think that true love might prevail and then suffer the harsh consequences of their actions, up to torture, execution, dismemberment, possible castration? Oof!

Treachery
And of course, with all these alliances rearing their heads, there’s the real possibility of treachery. Like love growing from hate, treachery is a big, big focal point in literature going all the way back to the fucking Bible and Gilgamesh.
In grimdark, treachery is so expected that if a character is true to your protagonist through the end and doesn’t die, it should come as a shock. Hidden enemies (like enemies in the open) are everywhere.
The best grimdark books don’t tell you that. They just show you. That nice but smarmy guy who was your wife’s friend when they were kids looks like he’s helping you out, right? You don’t figure out no until you’re being hauled away by the guards. The vizier who was raised alongside you like a brother plunges his knife in your back. The woman you fell in love with sells you into slavery. From your perspective, you don’t see it until the moment of treachery.
If the traitor is a point of view character, get ready for some juicy internal conflict leading up to the eventual backstabbing. Or, none at all if the traitor really, really hates their victims’ guts.

Can you really trust anyone?
Of course, this leads us to the million-dollar question above. A fundamental cornerstone of all human relationships is trust. However, in circumstances where that trust can be broken, when you’re in a high stakes situation, that trust isn’t guaranteed. Paraphrasing Squid Game, “I don’t trust you because you’re trustworthy; I trust you because I have no other choice.” Sometimes, you just need to build alliances with whoever you can. But beware: even if your radar for reading people is spot-on, they can still surprise you.
Alliances in the grimdark are less tribal and more fluid, usually. There are exceptions, especially where external circumstances come into play, like family, nationality, occupation, etc. And this in itself can be rife with conflict, especially if family ties get in the way of an alliance, organizations get in the way of love, and so on and so on. Sometimes the only one you can trust is your arch nemesis—at least you know where they stand!
It just goes to show that in the grimdark, the social order and the web of relationships through the story aren’t there just for the sake of the protagonist to overcome. They’re just there to navigate. Learn to play by the unwritten, ever-shifting rules, including being careful about who you trust, or you’ll lose.
What betrayal in grimdark stories do you think was the most well-written? Which were the most unexpected? Which inevitable betrayals still hurt the most?

As a fan of the grimdarkest kind, you might enjoy (vicariously) living in a world where not even the gods and their priests can be trusted. Read Raven Queen, Arise in Kindle Unlimited, paperback, or hardcover and see for yourself that our timeline on Earth isn’t the worst possible world.
If you’d like a free read, you can get the novella Death Descends for free just by joining my newsletter and navigate through the underworld with Z’nnek as he struggles to rescue his dead wife from the three demon lords of the underworld.