1)

He was immediately chained and handcuffed; and thus, without a moment's warning, he was snatched away, and forever sundered, from his family and friends, by a hand more unrelenting than death. (chapter 3)

In this first quotation, Douglass personifies slavery by describing it as "a hand" that reaches into families and snatches people away. Slavery doesn't literally have a hand, but personifying it in this way creates an impression that it has become some sort of malevolent creature. We sometimes hear people refer to "the hand of God" to imply God's omnipotence and closeness. In the same way, Douglass suggests that slavery is powerful and always close, ready to snatch loved ones away at a moment's notice.

2)

Slavery proved as injurious to her as it did to me. When I went there, she was a pious, warm, and tender-hearted woman. There was no sorrow or suffering for which she had not a tear. . . . Slavery soon proved its ability to divest her of these heavenly qualities. Under its influence, the tender heart became stone, and the lamblike disposition gave way to one of tiger-like fierceness. (chapter 7)

In this second quotation, Douglass is talking about his master's wife, Mrs. Auld, whose personality fundamentally changes because of slavery. The point Douglass is making is that slavery can harm—although in very different ways—both its victims and its perpetrators. Whereas Mrs. Auld used to be kind and charitable, she became cold and fierce.

The first figure of speech used is the metaphor "the tender heart became stone." Mrs. Auld's heart, of course, didn't literally become stone, but the metaphor serves to highlight how cold and inhumane Mrs. Auld became. A rock is, after all, a cold, hard, unfeeling object. The metaphor thus serves to emphasize the point that slavery dehumanizes both the victims and the perpetrators.

There are also similes in the last sentence of the quotation, where the pre-slavery Mrs. Auld is compared to a lamb and the post-slavery Mrs. Auld is compared to a tiger. The former connotes innocence and tenderness, and the latter connotes ferocity and aggression. The two similes, therefore, provide a stark contrast to show the extent of Mrs. Auld's transformation.

3)

They came because they wished to learn. Their minds had been starved by their cruel masters. They had been shut up in mental darkness. I taught them, because it was the delight of my soul to be doing something that looked like bettering the condition of my race." (Chapter 10)

In this third quotation, Douglass reflects on the slaves who came to his school. He again uses personification, this time to describe their minds as "starved," connoting images of malnourished, emaciated bodies. Given that the striking and appalling physical impacts of slavery are more easily depicted than the psychological, Douglass highlights slavery's psychological impacts by personifying the mind here, likening it to images of starving bodies which we can all, unfortunately, imagine.

The metaphor that "they had been shut up in mental darkness" adds to the image of a starved mind by connoting the emptiness and darkness of a prison cell. One might, therefore, imagine the mind of a slave as an emaciated body chained up in the darkness of a prison cell, left to decompose.

Douglass uses a variety of figures of speech in his Narrative, one of which is apostrophe.  Near the middle of the Narrative, Douglass stands on the edge of the Chesapeake Bay and offers an emotional outpouring to the ships passing by.  He praises the sense of freedom that the ships have in lines like:  "You are loosed from your moorings, and are free. . . ."  Douglass personifies these ships and then implicitly compares his own state of enslavement to these free ships out on the water.  This apostrophe is quite long, and Douglass becomes increasingly emotional over the course of it.  Based on the language Douglass uses, it is clear to the reader that Douglass is wishing for his own freedom, but he couches his personal desires in the personification of the ships (likely to protect himself).