Excalibur
Excalibur dismantles Black Air, Mountjoy, and the London Hellfire Club while the X-Men unlock the Xavier Protocols.
Collects The Uncanny X-Men #287-337, X-Men #53-57, Onslaught: X-Men #1, Excalibur #100, Wolverine #104, Cable #35, Onslaught: Marvel #1, Onslaught #1-6, Onslaught: Epilogue #1, X-Men / Avengers: Onslaught Omnibus. The full Onslaught saga -- Professor Xs dark side manifests as a world-ending threat.
Collects X-Man #18, X-Force #57, Excalibur #100, Wolverine #104, X-Factor #125-126. Onslaught assault ripples across the X-books as the teams scramble to respond.
Collects X-Man #15-19 and material from 14 other series. The complete Onslaught saga - Xavier dark psyche merges with Magneto rage.
Collects Excalibur #68-103, Excalibur Annual #1-2, X-Men Unlimited #4, X-Force #38, X-Factor #106, X-Man #12. The complete latter half of Excalibur through Warren Ellis's transformative run.
Collects Excalibur #96-103. Ellis concludes his acclaimed Excalibur run with the centennial issue.