In just two lines, "Home" makes a startling claim: that hellfire, of all things, is where the speaker feels at ease. Hell is normally the place we dread, so calling it "comfortable" is deliberately jarring. The speaker seems to describe a place or situation that looks unbearable from outside but feels familiar from within.
The second line widens the picture. The "dying star who gave us life" suggests the sun, which both created and sustains us, yet is also burning itself out. Its heat is "impossible," and still we are at home in it. Judging by this image, the speaker may be saying that the things that nourish us are often the things that hurt us, and that we get used to the pain because it is where we come from.
The mood is calm but unsettling. The tone is matter-of-fact, almost accepting, which makes the idea of a doomed, burning home feel quietly haunting rather than loud or dramatic.