To gain access, Shantae must give the Golden Pickaxe to the workers directly to the right of of Tan Line Temple. From there, simply continue to the right until she reaches the hole in the ground.
ScorpGals and giant Mantises roam in various areas of the labyrinth. The main puzzles here consist of spiky platforms that temporarily turn upside down when struck, creating safe footholds.
The first is seen immediately upon entering the Den, but Shantae initially cannot get it. Once she has the scimitar, she can break the blocks in the floor and walk through the walls to reach it.
The second is in the upper-left corner of a large room of spiked platforms on the east side of the map. It is very easy to overlook.
The last one is in the vertical chamber that is filled with breakable blocks. The Heart Squid is hidden in the block at the lowest-left corner.
Squid Baron (Reoccurring Rascal/Concerned Parent) is the boss of the Catacombs. This fight is rather similar to the fight in Risky's Revenge but also has some new tricks
When Squid Baron dashes through the room jump to dodge, you can also try using the Scimitar to both cause damage to him and dodge simultaneously.
Avoid being crushed by him when he drops from above, jump and use Risky's Hat when needed to avoid the shockwaves created by the impact of him falling.
When the Squid Baron starts eating he keeps on regaining health, spam him with your best attacks to make sure he doesn't recover much. Each time he eats, he regains up to 50 HP.
After receiving enough damage he will pause for a moment, then resume the fight as "Squid Baron 2.0". He will hide in a suit of metal armor that you have to break using the Scimitar before attacking him, otherwise all your attacks will be fruitless. He can do this again and again so slice that shield in half ASAP whenever he does that.
His attacks also speed up and are taken to a more extreme level, no changes are added so keep on dodging and attacking till he is defeated.
Both phases have 400 HP each, excluding any healing, so don't forget to get Silky Cream to knock down his health in large portions when he pauses in between attacks.