The Tunneler is an enemy in Final Fantasy IV -Interlude-.
Aside from a weak physical attack, the Tunneler can cast Earthquake, which hits all party members, and can use Constrict. Fortunately their HP is low and can be easily defeated within a couple of hits. It should be noted that it has a chance of dropping Silver Apples.
A stronger version is later fought in the Lower Section of the Tower of Babil as one of four Eidolon-holding bosses in a fixed encounter with buffed-up stats. It counters all attacks with Earthquake while also using Earthquake and Constrict for its normal turns. Cecil alone should attack while Porom heals the party. Casting Haste on her so she can heal faster allows the option for Palom to join in the assault with his magic, as Porom will be able to keep up with the more frequent Earthquakes easier.