Go to the Cartographer in the Bazaar and get your Tattered Mousoleum Map restored for $160,000. This will take 5 days.

After 5 days collect your restored map from the Cartographer and head to the Catacombs if you are Legendary.

Cheese:
1) Radioactive Blue Cheese
Collect
as many RB potions as you can in the Lab. You will need a continuous
supply of Radioactive Blue cheese in the Catacombs.
When RB cheese goes stale it becomes Radioactive Sludge. This is automatically put into your crafting inventory.

2) Ancient Cheese
Crafting recipe: (6) Ionized Salt + (3) Stale Cheese = (3) Ancient Cheese
Crafting recipe: (3) Magic Essence + (6) Ionized Salt + (3) Stale Cheese = (6) Ancient Cheese
Stale
cheese is obtained when Brie, Swiss, Marble, Cheddar or White Cheddar
goes stale on your trap. It is automatically put into your crafting
inventory.
Ancient cheese has a better attraction rate than RB.

Arcane Traps:
1) Obelisk of Slumber (OoS)
Buy
the Obelisk of Slumber trap in the Catacombs General Store for
$316,350. Alternatively use the Bottomless Grave or Sinister/Ambrosial
traps until you can afford the Obelisk of Slumber. These shadow traps
are not advisable for the long term in the Catacombs.

2) Obelisk of Incineration (OoI)
Crafting recipe: (1) Obelisk of Incineration Blueprints + (1) Obelisk Parts + (1) Coal+ (2) Scrap Metal + (3) Splintered Wood
Buy the Obelisk of Incineration Blueprints from the Catacombs General Store for $45,079.
Obtain
the Obelisk of Slumber parts by using the Hunters Hammer on the Obelisk
of Slumber trap. (Do not smash your OoS until you have 1 piece of coal
and 2 scrap metal. This may take some time.)
Coal is dropped by Keeper and Scavenger mice.
Scrap Metal is dropped by Scavenger mice.
Splintered Wood can be bought from the Training Grounds General Store.

3) Arcane Capturing Rod Of Never Yielding Mystery (ACRONYM)
Crafting recipe: (12) Scrap Metal + (1) Onyx Stone + (3) Magic Essence + (1) Obelisk Parts + (1) Mysterious Blueprints

Buy the Mysterious Blueprints at the Catacombs Trapsmith for $632,700.
Obtain the Onyx Stone from the Master of the Dojo in the Pinnacle Chamber.
Obtain Magic Essence by using the Hunter's Hammer on Super|brie+.
The ACRONYM is by far the best trap to use in the Catacombs.

Loot:
The Front cover of Plankrun's journal is dropped by Keeper mice in the Catacombs

Extracted info from Amy Wong on MouseHunt Forums@FaceBook