Death Eagle .42 (DEATH EAGLE-.42 (デス イーグル フォーティートゥー), Desu Īguru Fōtītoū) is a form taken by the Demon Twin Guns once Death the Kid has achieved the completion of at least one Line of Sanzu and the team initiate a Soul Resonance.
It seems that the first time Kid awoke used this form, "BREW" appeared before him for unknown reasons, and allowed him to realise his first Sanzu Line since one of the functions of BREW is Soul Amplification. After this, he and the Demon Twin Guns used Soul Resonance and the guns evolved into Death Eagle.42.
This form significantly upgrades the calibre of Kid's usual shots, and upgrades the "soul-width" that the guns can fire their Soul Wavelength from the norm .38 to .42, which when techniques via this form have been used, is strong enough to break Mosquito's Darkness Discord and receiving little damage.
The Demon Twin Guns go through a transformation after Soul Resonance, resulting in a change of appearance. The barrel becomes notably more rectangular like that of a real-world Desert Eagle. At the beginning of the barrel just above the handle, there are black verticals lines that sport a horizontal eye over it. Other than the black grip panel, the rest of the gun seems to be silver. Across the long barrel quote the words "Death Eagle-.42", and under that it says "Death Military Industries" with a mask replicating that of Death's mask to the left of these sentences. There is also a small mask on the grip panel of the pistols. There are also the numbers "4242564" written near the trigger of the pistol, referencing Kid's relation to Death or maybe that he is a Death God.
- The base design and the naming of this form is most likely in relation to the real-world pistol, the Desert Eagle.