Game of Thrones: I am Dothraki, Not a Barbarian

The protagonist travels through the Dothraki Grass Sea and kills Drogo at the beginning.

Then he becomes the queen of the Andals, the Rhoynar, and the First Men, the ruler of the Seven Kingdoms and the protector of the entire Westeros and Essos continent, the Khaleesi of the Great Grass Sea, the Breaker of Shackles, the Unburnt, the Mother of Dragons, the Princess of Dragonstone, and the man behind Daenerys Stormborn:

the Whip of the Seven Gods, Rhallor.

...

Tywin looked at him with disdain: "When someone challenges you, you should resolutely respond with iron and blood... Gods above, what the hell is that?"

Janos Slynt: "It is said to be the Dardanelles Cannon, made of Valyrian steel, weighing 40,000 pounds, and can fire a thousand-pound iron bullet!"

Tyrion stared with his eyes wide open: "Damn it! It razed Storm's End to the ground! We must escape!"

"Fellow countryman, don't run! We only want money, not lives!" Rhallor flew in the sky riding the red dragon Migo, with a bandit-like and kind expression.