How does a chain veil the earth with darkness (or how might it help Satan in veiling the earth...? Chains are not especially opaque. A search for “veil” and “chain” in the Old Testament yielded these possibilities:
If these words were actually used in a Hebrew document (say, on the brass plates), then Satan’s chain, a rābiyd, wouldn’t necessarily be something that looks frightening but could be ornamental and attractive, the kind we might gladly receive and wear around our necks with pride, only to realize too late that, like the golden handcuffs we speak of in the business world, it limits our freedom. Satan’s pretty chains are chains of slavery. They connect us to his crushing yoke and lead us captive into bitter servitude.
These two ideas (the chain as an adornment and the "veil of darkness") fit in very nicely with a few additional relevant Book of Mormon passages. First a connection to Nephi's discussion of the devil's "flaxen cord" at the end of 2 Nephi:
And there are also secret , even as in times of old, according to the combinations of the , for he is the founder of all these things; yea, the founder of murder, and of darkness; yea, and he leadeth them by the neck with a flaxen cord, until he bindeth them with his strong cords forever. (2 Nephi 26)
Note here the reference to two separate cords: First the flaxen cords, then the strong cords.
This paper by Gregory Smith explores the context of the term "flaxen cord" in exquisite detail. Among many other points, he finds very specific connections between 2 Nephi 26:20-21 (the two verses immediately preceding the verse quoted above) and major themes of 2 Nephi 28. Smith then (convincingly, in my opinion) connects verse 22 with 2 Nephi 28:21:
And others will he pacify, and lull them away into carnal security, that they will say: All is well in Zion; yea, Zion prospereth, all is well — and thus the devil cheateth their souls, and leadeth them away carefully down to hell.
Imagine that--carnal security as the flaxen cord with which we willingly bind ourselves, only to end up bound by Satan's strong cords before we realize it. If the flaxen cord is an "adornment" that we put on ourselves, that fits very neatly into this context.
Second, a connection between the "veil of darkness" and Nephi's discussion of "the two churches" in 1 Nephi 14. In this passage, Nephi makes extensive contrasts between the church of God and the "whore of all the earth." Visually, I picture the contrast between Christ as the Bridegroom, leading the church of the Lamb of God down safe paths, as opposed to Satan leading the "whore of all the earth" as a captive, covered in a dark veil, against her will down to hell. It fits in this context, too, and it is a stark image.
In light of all of this, what role does carnal security play in the Gospel? I'm reminded of a few New Testament passages:
31 Therefore take no thought, saying, What shall we eat? or, What shall we drink? or, Wherewithal shall we be clothed?And this one:
32 (For after all these things do the Gentiles seek:) for your heavenly Father knoweth that ye have need of all these things.
33 But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you. (Matthew 6)
16 And he spake a parable unto them, saying, The ground of a certain rich man brought forth plentifully:
17 And he thought within himself, saying, What shall I do, because I have no room where to bestow my fruits?
18 And he said, This will I do: I will pull down my barns, and build greater; and there will I bestow all my fruits and my goods.
19 And I will say to my soul, Soul, thou hast much goods laid up for many years; take thine ease, eat, drink, and be merry.
20 But God said unto him, Thou fool, this night thy soul shall be required of thee: then whose shall those things be, which thou hast provided?
21 So is he that layeth up treasure for himself, and is not rich toward God. (Luke 12)