A sand-snail, with a red body and grayish shell. This enemy likes to attack with a fast, electrified tackle.
When influenced by a Timeshift Stone, it regresses into an Ampilus Egg. You can then use the Hook Beetle to pick it up and place it where you want.
How to Defeat
Shield bash it to stun it (not with the Iron Shield), then proceed to defeat it with your sword. Aerial bomb attacks with the Hook Beetle also work.
In the cases where the monster was on quicksand, you can temporarily stand on the shell it leaves behind, to use it as an island while regaining your stamina.