Given that this

is the sigil of the Baratheons, the dead stag might well foreshadow Robert’s eventual death

He adopts this posture as a sign of respect, indicating that he understands the seriousness of the decision to take a man’s life

Ice is a Stark family heirloom, a (two-handed) greatsword made of Valyrian Steel

The sheer terror of encountering these creatures has left him slightly deranged

These words are delivered in a very ominous basso profundo— appropriately enough, given that they are the first to suggest, however obliquely, that Jesus' life is at stake

The fanatical John the Baptist had been beheaded by Herod for similarly disturbing the peace and decrying evildoers.

This title accurately depicts Jesus' self-contradictory nature: the manual labourer and supreme ruler are one. Also analogous to the union of divine and human natures in his person.

A viceroy is a monarch’s representative in a subject nation (e.g. the Governor General in Canada); he has similar but lesser powers to the sovereign.
In the metaphor of the conquered town, Reason is the ruler of the city, but cannot fight off the evil invader.

Likewise, Donne suggests that our reason serves a lesser but Godlike function in guiding and ruling us morally, logically, etc.

Christians believe in a triune God, who has three persons but is somehow essentially one in being. These persons — the Father, the Son, and the Holy Ghost — form the Holy Trinity. The classic (though rather simplified) illustration of this concept is the shamrock— supposedly employed by St. Patrick in the 5th century.

The Thames river was once so horribly polluted it was declared biologically dead. As this article explains, it has since undergone a massive transformation.