The Curse Of Longing is the combo Boon players can find, which uses the powers of both the God of War and the Goddess of Love. To activate this, Zag needs to have:

Ares: Curse of Agony or Curse of Pain.
Aphrodite: Heartbreak Strike, Heartbreak Flourish, Crush Shot, or Passion Dash.

It constantly inflicts Doom damage (Ares' main status effect) on all opponents who have the Weak status effect (used by Aphrodite). By default, Doom effects only proc once for a big burst of damage, so getting a Boon that can guarantee it'll proc multiple times can elevate a build from decent to overpowered in an instant. The only downside is that each successful Doom damage trigger has its damage nerfed by 50%, but it would be sort of broken otherwise.

This Boon comes from the party God of Olympus and King of the Seas. It is one of the strongest Boons in the game, simply because it improves all future Boons found in that run. To get this, Zag needs to obtain:

Dionysus: Drunken Strike, Drunken Flourish, Trippy Shot (Trippy Flare), Drunken Dash, or Dionysus' Aid.

Poseidon: Tempest Strike, Tempest Flourish, Flood Shot, Tidal Dash, or Poseidon's Aid

Exclusive Access guarantees that all further Boons gained will be of Epic rarity, at minimum. The earlier the player finds it, the better; but even if this is found in Elysium, this Duo Boon is still a must-grab.

This ability comes from getting abilities from the pompous King of Olympus and the humble Goddess of the Hunt. Compared to some of the other Duo Boons on here, this one is a bit more niche, but it's shockingly strong if used correctly. For Zagreus to use it, he needs to find:

Zeus: Lightning Strike, Thunder Flourish, Thunder Dash, Electric Shot, or Zeus' Aid

Artemis: Deadly Strike, Deadly Flourish, True Shot, Hunter Dash, or Artemis' Aid

Whenever Zag uses his Cast, a Bloodstone is used. When those Bloodstones pop out of the enemy, they land on the ground waiting for Zag to pick them back up. But with Lightning Rod, those Bloodstones now continuously hit nearby enemies with Lightning Damage once per second. This isn't a Duo Boon that immediately propels Zagreus into overpowered territory, but it does mean he'll have fantastic crowd control for the rest of the run.

The Hangover status effect inflicted by Dionysus Boons is one of the strongest effects in the game, and Low Tolerance makes it even better. To get Low Tolerance, Zag needs to get both Aphrodite and Dionysus to work together by getting one of each of their Boons. More specifically:

Aphrodite: Heartbreak Strike, Heartbreak Flourish, Crush Shot, or Passion Dash

Dionysus: Drunken Strike, Drunken Flourish, Drunken Dash, or Dionysus' Aid

By default, an enemy can get a max of 5 Hangover stacks on them at once, but this Duo Boon ups that cap to 8, as long as they're also inflicted with the Weak status effect as well. This means players can both massively debuff the enemies around them with Weak, as well as infect them with tons of passive damage thanks to Hangover as well.

This Duo Boon comes from the unlikely pairing of both Athena and Artemis, two strong Olympic Goddesses. To get it, players have to get:

Athena: Divine Strike or Divine Flourish

Artemis: Deadly Strike, Deadly Flourish, True Shot, Hunter's Flare, or Artemis' Aid

For players who are going for a full Artemis Build with tons of crit chance and crit damage, there’s no better Duo Boon to get. It triggers on every Deflect (the trademark effect seen in Athena Boons) and gives Zagreus 2 seconds of +20% Critical Chance each time. It elevates an Artemis Build to the next level, and adds even more utility to the already useful Athena Deflection Boons.

These two Gods on Olympus hold domain over two elements: ice and lightning. Zeus and Demeter work together for once to give Zagreus the Cold Fusion Duo Boon, and all he needs to have a chance at it appearing are:

Demeter: Frost Strike, Frost Flourish, Mistral Dash, or Demeter's Aid

Zeus: Static Discharge

This Duo Boon impacts the “Jolted” Mechanic that is a part of some of Zeus’ Boons. For a long time, players were confused as to how exactly Jolted enemies took damage, but now it’s known for sure. Once an enemy is Jolted, they’re briefly stunned and then take a big burst of damage the next time they try and attack.

With the Cold Fusion Boon, this Jolted status effect no longer wears off after one attack; rather after, a certain amount of time. This means that enemies who attack rapidly — such as, say, Hades himself — take this burst of Jolted damage over and over while the Jolted effects are active.

Hunting Blades combines the ultimate Warrior with the ultimate Hunter to turn Zag's Cast into an even faster-swirling rift of death. To activate this Boon, he'll need:

Ares: Slicing Shot

Artemis: Deadly Strike, Deadly Flourish, Hunter Dash, or Artemis' Aid

With this Boon, Zagreus has a Cast that can output an ridiculous amount of damage as well as reach them quicker, and it even gets ahoming effect as well. That said, the "seeking" ability only lasts about 3.3 seconds so it won't hunt down enemies infinitely, but still long enough to take out even the tankier mobs of the Underworld.

Normally the knock-away effects gained from the God of the Sea aren't highly sought after by Hades players, but with this Duo Boon that borrows some of the Lightning God's power as well, it's a totally different story. As usual, for this Duo Boon to appear, Zag needs:

Poseidon: Tempest Strike, Tempest Flourish, Flood Shot, Tidal Dash, or Poseidon's Aid

Zeus: Lightning Strike, Thunder Flourish, Electric Shot, Thunder Dash, or Zeus' Aid

This Boon ensures that any enemies knocked back by Poseidon Boon effects will also be struck by lightning. This applies to any knock-away effect, whether it's a Cast, Attack, or Special. Any fool who dares come near the son of Hades will be thrown away and shocked, in quick succession. Paired with Malphon or Stygian Blade, Zagreus is almost invincible in close combat.

While this next Boon is not as flashy as some of the others in this list, it is very powerful and will be very helpful to anyone aiming for a build to reach the end. It seems odd that a Duo Boon made up from the two most eccentric Gods isn't flashy, but maybe they just cancel each other out. Once again, Zag will need:

Aphrodite: Heartbreak Strike, Heartbreak Flourish, Crush Shot, Passion Dash, or Aphrodite's Aid

Poseidon: Tempest Strike, Tempest Flourish, Flood Shot, Tidal Dash, or Poseidon's Aid

This makes all the Poms of Power that appear from this point on more effective. Essentially, every Boon upgraded with a Pom gets +2 levels instead of +1.

Ice Wine is another great area control Boon made from arguably the least likely duo, Demeter and Dionysus. The Boons the player needs to obtain this are:

Demeter: Frost Strike, Frost Flourish, Mistral Dash, or Demeter's Aid

Dionysus: Trippy Shot

This makes the Festive Fog left by the Dionysus Cast ability inflict a Chill effect in that area as well and also increases the blast damage of this Cast as well. of the Cast. The Festive Fog was already overpowered enough since it stunned enemies inside and applied Hangover. Now that it inflicts Chill as well, it becomes a prison cell for any enemy caught in it, one that slowly kills them over time.

Smoldering Air, the Duo Boon made up of Aphrodite and Zeus is a bit of a mixed bag, as its usefulness is highly dependant on Zag's build. The component Boons needed for this to appear are:

Aphrodite: Heartbreak Strike, Heartbreak Flourish, Crush Shot, Passion Dash, Aphrodite's Aid

Zeus: Lightning Strike, Thunder Flourish, Electric Shot, Thunder Dash, Zeus' Aid

To put it simply, this Boon caps the God Gauge a 25%, meaning Zag can no longer use Greater Calls for the rest of the run. But, in exchange, the God Gauge now automatically fills itself. With certain Call Aids, like Aphrodite's or Zeus's, ironically enough, it's very useful since the "Greater" version isn't all too different. But, with other ones like Artemis' or Poseidon's, it might not be the best idea to pick this Duo Boon up.

Stubborn Roots, the product that comes from the two most "no-nonsense" Olympic Gods Demeter and Athena, is a great tool late in a run when Zag's Death Defiances are almost gone. For it to appear, Zag needs:

Athena: Divine Strike, Divine Dash, Athena's Aid

Demeter: Frost Strike, Frost Flourish, Demeter's Aid

Once Zag is completely out of Death Defiance/Stubborn Defiance, this Boon ensures he regenerates 1 life every 0.8 seconds. It's not a Boon that players will be desperately searching for in a run (unless they're a hell-mode player), but when it pops up they should still absolutely grab it since this HP regen can mean the difference between a frustratingly close run and a satisfyingly completed one.