Ohhh, you need to find the key!
Keep going east until you find a crypt full of zombies.
Explore the crypt, open the secret passage, and get the key.
You can then put the key in that 'barrel' as you call it, and open the rest of the cave!
I cant find the secret passage, i already beat the necromancer leader, is it near that ?
Nope, the secret passage is actually very far away from that, in the starting cave just south of Wimborne.
