Fedallah, the Zoroastrian (more specifically, Parsee), is the single most sinister and ominous character in Moby-Dick - just watch his eyes:
But did you deeply scan him in his more secret confidential hours; when he thought no glance but one was on him; then you would have seen that even as Ahab's eyes so awed the crew's, the inscrutable Parsee's glance awed his; or somehow, at least, in some wild way, at times affected it. Such an added, gliding strangeness began to invest the thin Fedallah now; such ceaseless shudderings shook him; that the men looked dubious at him; half uncertain, as it seemed, whether indeed he were a mortal substance, or else a tremulous shadow cast upon the deck by some unseen being's body. And that shadow was always hovering there. For not by night, even, had Fedallah ever certainly been known to slumber, or go below. He would stand still for hours: but never sat or leaned; his wan but wondrous eyes did plainly say - We two watchmen never rest.
Because Fedallah is a lightly sketched character, more of a foil to Ahab than a full character of his own, he lacks the softening depth of Ahab. Daggoo, by contrast, is a light-hearted charcater, though Daggoo is also a character of royal bearing and deportment. However philosophical Daggoo's scenes, there is usually a comic element, as when he lifts Flask on his back to get a better view of a whale sounding:
But the sight of little Flask mounted upon gigantic Daggoo was yet more curious; for sustaining himself with a cool, indifferent, easy, unthought of, barbaric majesty, the noble negro to every roll of the sea harmoniously rolled his fine form. On his broad back, flaxen- haired Flask seemed a snow-flake. The bearer looked nobler than the rider. Though truly vivacious, tumultuous, ostentatious little Flask would now and then stamp with impatience; but not one added heave did he thereby give to the negro's lordly chest. So have I seen Passion and Vanity stamping the living magnanimous earth, but the earth did not alter her tides and her seasons for that.
Like Queequeeg, who was born a prince in his native land, Daggoo will be seen throughout as an ennobled savage; good humor and regal bearing are almost always nearby when Daggoo appears. DH Lawrence makes much of the scene above, casting it as a commentary on American slavery, and Daggoo does overlap with a very different "chorus" of characters, the African-American characters, which include Pip and Cook, both notable in their own right and to be discussed in more detail later. However, I like to imagine that many of the paradoxical descriptions that abound in passages dealing with the "savage nobles" could be attributed just as much to the Jacksonian shadow that lay over Melville's America, and that that demagogic democrat (and Indian hunter) hides underneath the curtains of many a white characters' dress.
Finally, Tashtego is the last of the harpooners; Tashtego is sharp-eyed and attentive, and tends to spot things of the greatest relevance, whether they be whales or secrets. As a native American, you will find he also plays a role in Melville's thoughts on America and Americans. The fact that another native, Flask, of Tashtego's same mother island, Martha's Vineyard, is among the white officers is no accident.
Throughout Moby-Dick, the harpooners regularly serve as catalysts for deeper philosophic dives about the savage and civilized or the aristocratic and the democratic, though there is never a simple contrast and the harpooners are cast as the civil as well as the savage. In Typee, Melville consistently beat the drum that the civil were the savages and the savages the civilized. Here, however, those ostensibly civilized and ostensibly savage each engage in a complicated dance with good and evil, and neither has special access or monopoly to either. As Queequeg says when his hand is nearly bitten off by a shark:
"Queequeg no care what god made him shark," said the savage, agonizingly lifting his hand up and down; "wedder Fejee god or Nantucket god; but de god wat made shark must be one dam Ingin."