The Hirogen episodes continue, and again it's worth watching, this time as much for the Hirogen themselves (featuring Star Trek veteran Tony Todd) as the first appearance of Species 8472 since the two-part "Scorpion" (and thus the beginning of the season).
Species 8472 was not only the one threat the Borg couldn't handle, but also one of the first purely CGI aliens, so they were more alien than most aliens, didn't have speaking parts, and so mainly represented themselves by way of reputation. That the Hirogen obsessed over them wasn't a surprise. "Prey" is more about the Hirogen than it is Species 8472 (this is the least important appearance for them), but it's worthwhile viewing for crossing both in one episode, and therefore a good episode to watch for fans of the series.
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Memory Alpha summary.