There are four challenges with five ranks each. The challenges each contribute towards 100% game completion. Upon completing all ranks of all four challenges, the player is rewarded with the Legend of the Apocalypse Outfit. Completing the Undead Hunter and Four Horses of the Apocalypse challenges also unlocks the Unicorn.
Each challenge is described briefly here. For more details, including tips, please visit the individual challenge pages that are linked from each section.
- Main article: Undead Hunter Challenges
- Rank 1: Kill 100 Fresh Undead and 25 Bolters.
- Rank 2: Kill 25 more Bruisers and 15 more Retchers.
- Rank 3: Use a single explosion of a Retcher to kill 2 other Undead.
- Rank 4: Kill 2 Undead bears, 5 Undead wolves, and 3 Undead cougars using a torch.
- Rank 5: Find and kill a Chupacabra.
Undead Treasure Hunter
- Main article: Undead Treasure Hunter
This challenge requires the player to find buried treasure with the help of treasure maps.
- Main article: Undead Sharpshooter
This challenge requires the player to perform sharpshooting feats against Undead enemies.
- Rank 1: Kill 5 undead in 10 seconds using a gun.
- Rank 2: Headshot 10 undead in a row.
- Rank 3: Kill 5 flaming undead in one dead eye meter.
- Rank 4: Kill one of each undead type in one dead eye meter.
- Rank 5: Get 5 sniper kills on the undead in 8 seconds (without dead eye).
Four Horses of the Apocalypse
- Main article: Four Horses of the Apocalypse
This challenge requires the player to find and successfully break each of the four horses of the apocalypse.
- Ranks 1-4: Finding and breaking each horse of the Apocalypse.
- Rank 5: Kill each type of Undead with Death.
Completion of Undead Nightmare Challenges contributes towards the acquisition of the following Trophies/Achievements:
Attain Rank 5 in all Undead Nightmare Challenges.
Attain 100% Game Completion statistic in Undead Nightmare.