Game of Thrones is a series built on enmities: brutal showdowns on the battlefield, sudden acts of treachery or violence, and long-standing grudges between powerful families.

But given how deadly the show's political landscape can be, it's striking how often the final blow comes from what seems to be an ally. Robb Stark was killed at a festive wedding, despite a sacred oath that he wouldn't be harmed, by one of his closest advisors. Joffrey Baratheon's death was planned and executed by one of his councilors and his new grandmother-in-law. Jaime Lannister, the most trusted guard of Aerys Targaryen, killed the king by stabbing him in the back.

Westeros was built on the backs of those slaughtered bodies and broken vows. It's beyond cliché to say you should keep your friends close and your enemies closer — but in Game of Thrones, you might be better off without any friends at all. This week's "The Gift" sees many of the show's key characters — including Samwell Tarly, Sansa Stark, Margaery Tyrell, and Cersei Lannister — confronting the unforeseen dangers of the allies they have chosen.

Things have rarely been more tenuous or dangerous at the Wall, where the brothers of the Night's Watch are inching toward a full-scale civil war. The Night's Watch is built on an almost Arthurian ideal: a knightly brotherhood, loyal only to itself, tasked with guarding Westeros from whatever dangers lie to the north. It sounds noble on paper — but the reality, of course, is much different. Over the course of the series, the Night's Watch has grown increasingly divided, culminating in the coup that killed Jeor Mormont, the Lord Commander before Jon Snow.

Though Jon Snow asserted his authority by beheading an openly rebellious member of the Night's Watch, his decision to head north with the wildlings has put his closest ally, Samwell Tarly, in a precarious position. It's only made worse when his friend and advisor, Aemon Targaryen, dies of old age. "You're losing all your friends, Tarly," warns Ser Alliser, and he's right; within a day, his sworn brothers are beating Samwell and assaulting Gilly. With Aemon dead and Jon Snow gone, Samwell's only real ally is Jon's direwolf — not a bad creature to have in your corner, but hardly enough to fend off all the horrors both within and without Castle Black.

Down in Winterfell, the dangers are even worse, as Sansa adjusts to life as the imprisoned and unwilling wife of Ramsay Bolton — a position she only occupies because she placed her trust in Littlefinger. Littlefinger may not have known the true depths of Ramsay Bolton's sadism, which appears to have been a closely kept secret, but he knew enough to warn Sansa that her situation was as dangerous as anything she had faced. He left her in Winterfell anyway, without so much as a single guard from the Vale to protect her, which enables Ramsay to embrace his depravity without any checks whatsoever: locking Sansa in a bedchamber and raping her, without a single friend or ally who would even know how to track her down.

That utter alienation leads Sansa, in her desperation, to turn to Theon Greyjoy — the man who betrayed Robb Stark, her brother and his lifelong friend, and facilitated the Boltons' rise to power. But despite her appeals to whatever remorse or loyalty might be left in Theon, she can't reach him; he reveals her plan to Ramsay, who kills the hardy northern woman who promised to help Sansa if she needed it.

It's a brutally grim outcome, but it also gives Sansa all the information she needs to fall back on the one person she knows she can trust in Winterfell: herself. She openly taunts Ramsay about the possibility that he'll lose his inheritance as the Warden of the North once his new, legitimate half-brother is born, while quietly grabbing something she can use to attack him if she ever gets the chance. This isn't the first time Sansa has been prepared to inflict mortal violence on an abuser, and given the growth she's shown over Game of Thrones' five seasons, I wouldn't bet against her.

Back in King's Landing, Margaery Tyrell is grappling with the unforeseen consequences of Tywin Lannister's death. When Olenna Tyrell cut a deal with Tywin, it was a mutually beneficial political arrangement: the power of the Lannisters for the resources and stability of the Tyrells. But Tywin's death left a vacuum in the kingdom's true seat of power, leaving his daughter Cersei to take control of the throne in everything but title — and she has no intention of honoring the deal Tywin originally made.

Cersei's maneuverings have been remarkably successful; Margaery and her brother are locked in cells, awaiting trial, with no clear hope on the horizon. When King Tommen laments to his mother how frustrated he is at his inability to rescue his new queen, Cersei assures him she'll do anything to save Margaery. "Your happiness is all I want in this world," she says. "I would do anything for you. Anything to keep you from harm. I would burn cities to the ground." It's all true — but not in the way Tommen thinks. Cersei's love for Tommen is both all-consuming and all-controlling, and the "anything" she's willing to do includes lying to him, manipulating him, and ensuring that anyone who threatens her influence over him is eliminated.

But Cersei herself has made a grave tactical error in the ally she chose. The High Sparrow is a new and mysterious figure, but he seemed relatively content with the unspoken arrangement Cersei proposed: unrivaled power in exchange for a humiliating, damning public trial for the new queen. But Cersei was so busy setting the High Sparrow onto the trail of Margaery's sins that she never considered what he might think of her own. Cersei's cousin Lancel — a former lover — has wholly embraced the Faith of the Seven, and he's more than happy to provide testimony about Cersei's sins. As Cersei is thrown into a cell very much like the one to which she doomed Margaery, she tells the nun that she'll get her revenge. It's the desperate snarl of a cornered animal who's not willing to admit that she's already been defeated by a trap of her own devising.

All these unsuccessful, often self-destructive alliances make the big new pairing in "The Gift" look all the more promising. After dozens of episodes spent thousands of miles apart, Tyrion Lannister and Daenerys Targaryen — two of Game of Thrones' most beloved characters — have finally met. I try to stay away from comparisons between the books and the TV series — but as someone who slogged through every Tyrion and Daenerys chapter in A Dance with Dragons, waiting for a long-teased meeting that never actually came, it's hard to overstate how satisfying it is to see these characters come face to face for the first time in any version of this story.

It would be natural for Daenerys and Tyrion to distrust each other, but we've spent enough time with both to know that they're smart, capable, and loyal to their allies. If they can overcome the longstanding enmity between their families and focus on their mutual goals, they'll be ideal allies in the quest to restore some stability to war-torn Westeros, just as winter looms on the horizon.

Earlier this year, Ser Barristan warned Daenerys about the dangers of ruling in a bubble, without brilliant, trustworthy advisors to help weigh the pros and cons of each major decision. We've seen Tyrion thrust into a key advisory role before, when he served as King's Hand to his nephew Joffrey, and almost singlehandedly saved King's Landing with a brilliant tactical gambit. He knows Westeros, he knows politics, and he intimately knows most of the people vying for power. In short, he's exactly who Daenerys needs if she's going to continue her campaign for the Iron Throne — and there's never been more room on her Queen's Council.

Read more Game of Thrones recaps:

* Game of Thrones recap: 'Unbowed, Unbent, Unbroken'
* Game of Thrones recap: 'Kill the Boy'
* Game of Thrones recap: In the mood for love
* Game of Thrones recap: Goin' to the chapel
* Game of Thrones recap: 'The House of Black and White'
* Game of Thrones season premiere recap: 'The Wars to Come'