Returning to Westeros: Dany's Fleet (Spoilers Extended)

In order to get many of her troops to Westeros, Dany will likely have to make common cause with and give things to people that she doesn't want to. For example Barristan has already promised Pentos to the Tattered Prince. The Ironborn have arrived in Slaver's Bay and there is no way that Dany will be able to make use of the Iron Fleet without a bit of quid pro quo.

This little plot detail creates so much intrigue/drama because of the following:

• Dany isn't in Meereen during the Battle of Fire and the Ironborn have joined the fight
• Victarion has the dragonhorn
• The horn will work for its "master" (who must claim the horn with blood)
• Victarion has 3 thralls ready to blow the horn
• Both Euron/Victarion want to marry Dany
• Dany is married (to Hizdahr) and Victarion plans to kill him
• The Dusky Woman is present (Euron's gifts are poisoned)
• Rhaegal is last mentioned circling the bay (right about when the horn is going to be blown)
• Moqorro's allegiances are unknown (Dany, Benerro, etc.)

How this could be resolved:

a)Dragonhorn works for Victarion

Our boy Vicky is a dragonrider! (Assuming not for long).

Right as the horn is about to be blown we see Rhaegal creeping that way:

By the time Plumm and his companions came galloping back from the camp of the Girl General, the white dragon had flown back to its lair above Meereen. The green still prowled, soaring in wide circles above the city and the bay on great green wings. -TWOW, Tyrion I

b)Victarion and Dany marry

Victarion has already threatened to kill Hizdahr:

Come sunset, as the sea turned black as ink and the swollen sun tinted the sky a deep and bloody red, Victarion came back on deck. He was naked from the waist up, his left arm blood to the elbow. As his crew gathered, whispering and trading glances, he raised a charred and blackened hand. Wisps of dark smoke rose from his fingers as he pointed at the maester. "That one. Cut his throat and throw him in the sea, and the winds will favor us all the way to Meereen." Moqorro had seen that in his fires**. He had seen the wench wed too, but what of it? She would not be the first woman Victarion Greyjoy had made a widow**. -ADWD, The Iron Suitor

and it could potentially fit the "bride" section of the House of the Undying Vision:

A corpse stood at the prow of a ship, eyes bright in his dead face, grey lips smiling sadly. -ACOK, Daenerys IV

c)Victarion dies and Euron (via glass candle) negotiaties with Dany

The black priest bowed his head. "There is no need. The Lord of Light has shown me your worth, lord Captain. Every night in my fires I glimpse the glory that awaits you." -ADWD, Victarion I

d)Victarion dies and Moqorro/Iron Fleet give allegiance to Dany

This is possible, but due to Dany being gone during the battle it seems unlikely.

I'm sure there are other potential possibilities but the point is, the Ironborn leader (whoever you believe it to be) isn't just going to give Dany a war fleet.

TLDR: Victarion isn't leaving Meereen without a dragon/marriage to Dany (or both) so something has to give.