The Tunnels of Terror Add-on for Back 4 Blood has 12 achievements.
Complete All Ridden Hives.
Get a kill with a Legendary Weapon.
Earn some Skull Totems.
Kill 10 Ridden with a Skull Totem.
Kill each of the Warped Ridden
Find the Secret in The Nursery.
Find the Secret in Sunken Passages.
Find the Secret in The Cut.
Find the Secret in Brood Lair.
Find the Secret in 300 Below.
Find the Secret in Blood Stream.
Find the Secret in Caustic Cesspool.