1 And the king Ahasuerus laid a tribute upon the land, and upon the isles of the sea. 2 And all the acts of his power and of his might, and the declaration of the greatness of Mordecai, whereunto the king advanced him, are they not written in the book of the chronicles of the kings of Media and Persia? 3 For Mordecai the Jew was next unto king Ahasuerus, and great among the Jews, and accepted of the multitude of his brethren, seeking the wealth of his people, and speaking peace to all his seed.
[AD 856] Rabanus Maurus on Esther 10:1-3
That King Ahasuerus exacted tribute from all the islands, which is where the Hebrew version of the story of Esther comes to an end...

Why are we told that King Ahasuerus exacted tribute from every land, and from all the islands of the sea? Because the historical king of the Persians and Medes never held every land under his sway, and could not exact tribute from all the islands of the sea since not even his name could have reached the aforementioned islands and parts of the world; whereas this statement more accurately reflects our king and Lord Christ, whose power is in Heaven, and on earth, and on the sea and in all the depths. In fact, in the Gospels he calls himself a gateway, since through him we gain the entry to eternal life; and according to a statement of the Psalmist: “The whole world, all the kings of the earth, adore him. All the kings of the earth will serve him, the kings of Tarshish and the islands will offer him gifts, the kings of Arabia and Sheba will bring presents” (Psalms 72). So the strength, and power, and dignity, and grandeur of this king, and how he raised up the true Mordecai—that is, the community of sacred teachers who were leaders of the Church at the head of the Christian people—are documented in the statements and the writings of not only the single people of Judea, but of all the nations as well. He has from the start exalted his chosen ones with the gift of his grace, and has glorified and honored them in the sight of all the nations; these seek the best for their people and whatever they say is concerned with the well-being of their seed, since according to the prophecy of Isaiah: “The watchmen of the Lord will lift up their voices, and will praise altogether (Isaiah 52); their feet are beautiful, the feet of those who bring the gospel of peace, the gospel of good things” (Romans 10). This is because they always ask after the peace of Jerusalem, and their seed will be known among the nations and their offshoots amid the peoples. All who have seen them will know them, because they are the seed which the Lord has blessed.

[AD 856] Rabanus Maurus on Esther 10:1-3
What does the text mean when it says that King Ahasuerus made all lands and all islands of the sea subject to his tributes? Since the historical king of the Persians and Medes did not have all lands under his rule, nor was he able to make all the islands of the sea subject to his tributes since the fame of his name could not even reach some of those islands or parts of the world, this sentence more truly applies to our king and Lord Christ whose power is in heaven, on earth, over the sea and every abyss. And he called himself “door,” because through him we have access to eternal life, according to the testimony of the psalmist, “And the kings of the entire universe adore him. And all the kings of the earth serve him, the kings of Tharsis and the islands offer gifts, the kings of Arabia and Sheba bring gifts.” Therefore not only the voices and the writings of the Jewish people alone, but also those of all the nations testify how the power of this king, his authority, dignity and preeminence advanced the true Mordecai, that is, the assembly of the holy teachers and masters of the church who lead the Christian people. Those whom he made his elect at the beginning through the gift of grace, those whom he made glorious and honorable before all the nations are the ones who look out for the good of his people and speak the words which concern the peace of his seed, according to the prediction of Isaiah: “Listen! Your sentinels lift up their voices; together they sing your praises.”