Scarlet Turret first appears as a red shadow throughout the second section of the Tziah Block within Tartarus. It will be the subject of one of Elizabeth'srequests and will drop Red Armor Plates while the quest is active. Returning to Elizabeth with 2 Red Armor Plates will complete the quest.
The Scarlet Turret will later appear as a normal enemy in the Harabah Block, from floors 165 to 179.
The Scarlet Turret appears in the 9th Chapter of the Void Quest within the Midnight Channel. It will alternate between casting Agidyne and Mind Charge followed by Agidyne. They are a good candidate for Silence or Confusion skills to be utilized. After defeating it, it may drop the Super-Alloy material. Selling 4 Super-Alloys at Daidara will unlock the Alloyed Plate weapon for Kanji Tatsumi in the shop.
Red Shadows appearing in the 9th Chapter may be a group of three Scarlet Turrets.
In Golden, it appears in Chapters 6 through 9. It may also drop Bloodstone for trade at Shiroku Pub.