Harry Potter book 7 is Harry Potter und die Heiligtümer des Todes. Coincidence?
The similarities come because they both talk about death, which is, in German, "Der Tod". The "der" is simply "the", but in German, it indicates that the noun is masculine.
When you make it possessive, "of Death" becomes "des Todes", where "des" is the genitive (in practice, think possessive) form of "the" for nouns with masculine gender. It could also be translated as "of the death" except that we don't typically say "The death", unlike German.
The "und" is simply "and". So because both titles have "[Name] and the [item] of death" (in German, at least), there are going to be similarities between their titles. But most of the similarities are simply grammatical necessities in German. The content is in the blanks that are, in fact, different.
And yes, the "das" in the sentence is part of the noun phrase "das Pergament", which simply means "the parchment" ("pergament" is apparently neuter). "Das" can mean "that", but not in this context.
Incidentally, all my German is old missionary German, so while I've got the grammar, the vocabulary mismatch makes trying to read it a real pain.
