Spawn's body is quite dense, weighing over four hundred pounds, and is composed completely of necroplasm. This gives him super strength and durability. While he still has internal organs, they are non-functional, and their damage/destruction does not hinder Spawn in the least. These organs re-appear when he magically regenerates his wounds. This may be due to Spawn's inability to let go of his human self, retaining his human organs even though he no longer requires them.
Spawn wears a living symbiotic costume. His cape, spikes, chains, and skulls are all part of one organism that will protect Spawn even if he is unconscious. Violator once said the suits feed on souls. The true source of the costume is the necroplasm in Spawn's body, which it feeds off of. It is possible for Spawn to draw this energy back when he needs it, using it to power his abilities without draining his own reserves. The costume can also feed off evil energy from the physical world, feeding off the ambient evil of people, animals (mainly carrion insects, but also wolves and bats) and even certain parts of the city.
Spawn has vast magical powers. In the issues before issue #50, Spawn had a limited power supply or "9999". Each time Spawn used his energy, the counter would drain. Because of this reason, he relied primarily on his costume's natural abilities in fights. Other than the counter, the only limit was Spawn's imagination. Though he always tried not to expend a lot of magic, he has been shown using it for a variety of effects including resurrecting the dead, firing blasts of necroplasmic energy, teleportation, shapeshifting, and curing the sick.
Spawn has an ability to "feel" or "sense" misery. He is aware, even subconsciously when someone is attacked or murdered. Spawn typically travels in the shadows, even "flying" on occasion. He is often described as notoriously difficult to spot, often only caught out of the corner of one's eye as just a streak of red (his cape). Recently, Spawn has taken every other HellSpawn into himself and with the help of a young Spawn (Christopher), he is able to summon them for aid.