The Digger, Destroyer, and Sentry are a series of self-automated robots of De Loco's design. These enemies are palette swaps of each other, each with varying levels of strength and are fought in different locations in the game. This monster line is Yellow-affiliated.
Diggers are the most durable enemies that you are guaranteed to encounter in the mines, and their attacks can be quite powerful, even though their Attack stats is lower than the Mine Patrol's. Of course it is not as powerful as the seldom seen Serpantis.
A Destroyer (デ式レーダー De Shiki Reedaa) is a blue variant with a series of searchlights in place of a drill.
Unlike most other enemies in the game, Destroyers will not directly attack the party (therefore making their Attack stats a moot point). Instead they use the following battle commands:
Search: The Destroyer's front light lights up and surveys the area. However, this ability doesn't do anything else.
Call Allies: The Destroyer lights up and sounds an alarm that summons an additional Destroyer into the current battle. If this fails however, the lights will not turn on, and a clicking noise will occur.
Emergency!: An alarm sounds and all Destroyers in battle explode, thus removing them from the current battle and replacing them with a Kantor, a stronger palette swap of Antonio. This ability removes the Destroyers in a way that doesn't count as a kill (the party will not gain any EXP or Gold). This is an Expidited Ability which is an ability that takes effect before all basic combat techniques, regardless of quickness.
Each Destroyer the party manages to defeat yields 234 EXP and 139 Gold. Destroyers are fought in the Grand Fortress. While seldom fought as random encounters in the exterior portion of the fortress, they are mainly fought in scripted encounters if the player steps into one of the searchlights in the harbor area.
Without a means of attacking the party, Destroyers are really nothing more than punching bags. The only reason they should be destroyed quickly is to prevent them from summoning the Kantor.
The Sentry is stronger, but slower than the Elite Guard, though its not as strong or durable than the Berserker and Lurgel Tank. It's easy for the party to destroy them before they can use Discharge since it requires a turn to charge. Their immunity to Yellow attacks is something to keep in mind when fighting them, though conversely, they are more susceptible to Blue and Silver attacks than their predecessors.