Deception III: Dark Delusion, known as Soumatou (蒼魔灯) in Japan, expanded on the gameplay of Kagero: Deception II by introducing a training mode, a mission mode, and trap enhancement through a series of crests and other artifacts. In the main story mode, players control Reina, a girl who, with her adoptive family, has been kidnapped and brought to the land of Burgenhagen to be sold into slavery. Reina must use the trapping powers she acquired to defeat her kidnappers and solve the mysteries of the pendant she wears, which other people seem to covet for unknown reasons.
The aforementioned Free Training mode was simply a means of testing all of the available traps in a controlled environment with an immortal invader who could programmed to adopt behavioural patterns, to learn their effects and uses without any real consequences. In contrast, the mission mode, known as Expert Mode, assigned the player a given goal to achieve, usually within a time limit, with the traps available being any unlocked up to that point. Typical missions include, "Crush the invader with a 4-hit combo," or, "Make the killing hit a Pendulum trap." Also included is a Trap License mode which functions as a further tutorial, asking the player to perform various tasks that teach him or her the nuances of the game in the name of learning helpful tips or trap functions. Traps have been made even more customizable than in previous games through the uses of Base Circles, Orbs, Emblems, and Rings. Base Circles contained the variety of trap involved (Pendulum, Arrow Slit, Bear Claw, etc.); Orbs determined the power level of the trap, ranging from 1 to 4; Emblems gave the trap an element or special characteristic (Lightning, Fire, Slave, etc.); and Rings further enhanced a trap by increasing their power, shortening their charge time, or a myriad number of other changes. The more modifications a trap employed, the more "Dreak" (the replacement for Kagero's Ark) it took, but again, traps could be used infinitely upon creation. These elements make the an excellent example of the trap-em-up genre, which also includes games like Heiankyo Alien, Home Alone, and Night Trap. The loons from Kagero: Deception II also returned as the sole means of regaining lost hit points. While not having secret traps, special emblems and rings can be acquired by achieving the game's four endings. Game saves are one block in size.