To get the super weapon in Takoshima you need to get 30 artifacts, and all Arkvoodle cult missions in Albion, Bay city, and Takoshima.

Once you beat the last cult mission in Takoshima you go to the place in the Zen temple where the burrow beast datacore is located. It will appear on your radar as a purple dimond.

The burrow beast weapon shhots out a green lure and then you will see a trail of dirt leading to the nearest human then a huge worm like thing eats them then goes underground for the next human to eat. The lure will only last a while and you can pick it up with your PK and transmog it for ammo.