The 00s were a big decade for Hank. He developed a "second mutation" that made him more cat-like, nearly stole the show in Joss Whedon's "Astonishing X-Men," and found new love. His high point storywise, though, has to be "Endangered Species" and that statement probably goes for his entire existence as well. Released as a serial at the end of 16 different issues (along with a lead-in one-shot,) "Endangered Species" chronicles his search for a scientific solution to Scarlet Witch's M-Day declaration of "No More Mutants" which cut their population from tens of millions to less than 200.
Unable to find the answer himself, Hank is forced to seek the assistance of several shady characters, including the likes of Doctor Doom, Mr. Sinister, Arnim Zola and Spiral. He travels to Wundagore Mountain to visit the High Evolutionary: no solution. He visits the lab of would-be mutant gene "curer" Dr. Kavita Rao: no solution. The turning point in the series comes when Hank visits Neverland, a Canadian concentration camp for mutants. It's there that he finds arguably the most despicable scientist that exists in the Marvel Universe. What worse: he has Hank's own face, or a previous version thereof. Dr. Hank McCoy, the "Dark Beast" ripped from the Age of Apocalypse timeline.
As the original Beast's desperation mounts, he finds himself with no other choice than to work with his evil, morally-bankrupt counterpart who soullessly tortured thousands and believes the same course of action is required to restore the X-Gene worldwide. Their team-up is the heart of this series, as the two argue method, sometimes coming to blows and eventually tearing at each other's throats when Dark Beast goes too far. Original Hank's inner monologue as he violently slashes at his doppelganger is something else.
Having failed to find an answer in science, Hank - on his own again - searches for answers through magic, even other dimensions, ultimately ending up in the fictional country of Transia. Who does he find there? Scarlet Witch herself, appearing to be - or feigning to be - an amnesiac. Their meeting is unsettling and leaves Beast with a sense of hopelessness. Unbeknownst to him, the X-Men were about to find just that: Hope.
"Endangered Species" is exceptional episodic storytelling, particularly given the number of hand-offs involved. Mike Carey, Christopher Yost and Craig Kyle exchange writing duties without missing a beat, find a perfect voice for Beast, Dark Beast, Bishop, Kavita Rao and ALL of the villains. The material is engaging and thought-provoking. Also, for a 17-part series where each segment was short, it's damned near seamless and easily digested. The art, meanwhile, is consistently excellent, switching between five pencillers, led primarily by Scot Eaton. The changeovers are apparent, but are not drastic in the least. That's better than what most creative teams muster during most major crossovers, which is exactly what the X-line was priming for.