After the goblins retrieve Airain's Mushroom from the depths, they continue on to the spider cave.
How to Clear Gobliiins Level 6
Switch to 
Bobo/Asgard and make him stand next to the long spider
web. Then click the spider web to make him climb up. Then change the cursor
to a fist and click on the
rightmost short spider web and he will pull up the spider that is in the lower
part of the room.
Switch to 
Dwayne/Oups and change the cursor to an open hand.
Click on the pistol in the bottom-right of this area to pick it up. Then change
the cursor to a fist and click the spider that is covering the cave on the
right side of the room. The spider will move upward.
Then click the ladder under the sleeping spider in the upper-left part of the
room to make Dwayne/Oups shoot the pistol there.
The spider will wake up and go back up to the ceiling. Switch the cursor to an
open hand and click the pillow to take it. Then click the platform beneath
the middle spider (between the two bridges), to place the pillow there.
Switch to 
Hooter/Ignatius and change the cursor to a fist, then click
the spider that is above where you moved the pillow.
It will drop Arachnide's Elixir. Switch to
Dwayne/Oups and change the cursor to an open hand. Click
Arachnide's Elixir to take it.
If the level isn't complete, have Dwayne/Oups get the pistol
and use it beneath the spider on the right side of the room.
This completes the level. Click the flashing "Go" where the spider was. Make a note of the code in the bottom-left of the screen ( ), then click anywhere to continue to the next level, The Garden Field.