The Fangshell is an enemy in Final Fantasy IV. It usually appears together with Amoebas. While it may cause some problems if Rydia is underleveled, after Tellah joins the party these should be no problem. Cecil's high Strength should still allow him to slay one of these with the Attack command, even though Fangshells are resistant to physical attacks. With two Thunder casters these will be fairly easy to take down.