How are the witches presented in Macbeth?

In Macbeth, the witches are presented with a few distinct characteristics. Banquo describes them as looking "not like th' inhabitants o' the' Earth" (1.3.42). He also suggests that they have beards. In act 1, scene 3, Macbeth and Banquo happen upon the witches suddenly, which also suggests that the three weird sisters have the ability to appear as if from nowhere, but even before Macbeth's first interaction with them, Shakespeare establishes their demeanor in a way that reflects their strange appearance. At the start of this scene, the three witches are reconvening the meeting that was established at the very start of the play, and this exchange takes place:

First Witch: Where hast thou been, sister?Second Witch: Killing swine.Third Witch: Sister, where thou?First Witch: A sailor's wife had chestnuts in her lap, And munch'd, and munch'd, and munch'd— 'Give me,' quoth I: 'Aroint thee, witch!' the rump-fed ronyon cries. Her husband's to Aleppo gone, master o' the Tiger: But in a sieve I'll thither sail, And, like a rat without a tail, I'll do, I'll do, and I'll do.Second Witch: I'll give thee a wind.First Witch: Thou'rt kind.Third Witch: And I another.First Witch: I myself have all the other, And the very ports they blow, All the quarters that they know I' the shipman's card. I will drain him dry as hay: Sleep shall neither night nor day Hang upon his pent-house lid; He shall live a man forbid: Weary se'nnights nine times nine Shall he dwindle, peak and pine: Though his bark cannot be lost, Yet it shall be tempest-tost. Look what I have.Second Witch: Show me, show me.First Witch: Here I have a pilot's thumb, Wreck'd as homeward he did come.

This scene goes a long way in establishing the character of the witches. One of them just happened to be killing pigs before they met up. There is no mention of her being a butcher, so it seems like she was just doing this for fun. Further, the First Witch relates a story of a "great wrong" she has suffered. She saw a woman eating chestnuts and rudely demanded to have some. The woman told her to back off, and now because of that simple, brief affront, the witch is going to seek out the husband of the woman and torture him until he begs for death. As if that wasn't intense enough, she then shows off a finger of a dead sailor. Through this scene alone, we see the witches as more than just "weird." They are manipulative, they are evil, and perhaps scariest of all, they are petty. They behave terribly and then get mad at others for not responding as they want them to. Their entire manipulation of Macbeth also seems to be happening for no reason other than their own desire to watch his world collapse around him. They have nothing to gain from it. They simply want to watch the world burn.