The Evil Spirit Incarnate is the final boss of Metal Slug 5. Although its origins and purpose are unknown (the game makes no mention of its existence until the final battle), it is perhaps the true mastermind of the game's events, possibly manipulating the Ptolemaic Army through the white masks used by their cult leaders.
Only one thing is for certain: it's susceptible to conventional human weaponry, enough to send it packing after prolonged damage. So despite its fearsome appearance and notable strength, it's not all-powerful by any means.
The gigantic demon will cast energy spheres that track down the player. After a short time, it will cast a large amount of spheres and fly away. The demon's shadow will appear in the background, raising its scythe to target the player's position, giving a moments notice to get out of the way. Merely dodging the scythe is not enough, as it will create a spray of deadly arcing smoke projectiles upon impact with the ground.
Its weak spot is the skull on its chest. Once sufficiently damaged, several explosions will burst forth from the demon, and it will fly away - thus preventing us from ever knowing exactly what this behemoth was.
- To date, the Evil Spirit Incarnate has the largest sprite size in the series.
- The Evil Spirit Incarnate resembles the alternate flag of the Rebel Army. It also bears a passing resemblance to The Grim Reaper - given the occult nature of the Ptolemaic Army's doings, some fans believe the Evil Spirit Incarnate to be Death itself, given form and summoned to do Ptolemaios' bidding. Others think it is a demon of some kind, or possibly even the Devil. It could also simply be an extraterrestrial life form, given the starry night appearance of its "skin".
- At the beginning of the fight, the players' characters use their "chilly" animation, suggesting that the boss may have a cold body or that the battle takes place at a high altitude.
- A common name that the fans use for the Evil Spirit Incarnate is Scyther.
- In Metal Slug Attack, Ptolemaios (the native struck by lightning at the start of Metal Slug 5) may summon the Evil Spirit (in the background only) using an ability called "Geographia" - whether or not this is a reference to the demon's actual name is uncertain. In real life, it's the name of an atlus written by Claudius Ptolemy. Prior to this, some fans theorised that Ptolemaios and the Evil Spirit may've been one and the same.