One of Spawn's most notable features is his massive flowing cape. Dour and Gothic like the hellspawn that wears it, this cape is often shown surrounding Spawn like a set of protective wings. This look isn't just a fashion choice, however, as there's a symbiotic function to Simmons' evening gown.
Much like a certain other Todd McFarlane creation, Spawn's spike and chain-heavycostume is a living symbiote with powers and a mind all of its own. Powered by the same necroplasm as Spawn, this symbiote protects Spawn while also feeding off of his energy and spinal fluid. Here's the grisly history of this somewhat disgusting choice of clothing.
Spawn's Symbiote: K7-Leetha
Spawn's costume symbiote is named Leetha of the 7th House of K, or K7 Leetha. This female symbiotic parasite constantly evolves and changes as it grows and consumes energy, which it regularly does once attached to a host. The creature is made of necroplasm like the type that empowers Spawn himself, and it was forged in the fires of Hell. Though it theoretically debuted in the very first issue of Spawn, its presence and characterization were only first made known in Spawn: Blood Feud #1.
Like others of its kind, it bonds to its host for life unless otherwise forcibly removed. Upon attaching to said host, it feeds not only from the potential necroplasm that a host might provide, but also the spinal fluid and neural chemicals from their brain stem. This provides the symbiote with a telepathic link to its host, though this might not always manifest at initial bonding. This is why it took Spawn so long to figure out the truth behind his costume. This connection extends to the host's subconscious and possibly even their soul.
The Powers of the K7-Leetha Symbiote
K7-Leetha and other symbiote costumes have incredible abilities, which are sometimes confused as built-in powers of their hosts. For one, the symbiote constantly evolves and grows over time, causing its natural form to change as well. This is why Spawn's costume changed after the first few years of the comic book.
The costume can also shapeshift, which has given Spawn camouflage and shapeshifting powers of his own. This is also the reason for Spawn's hardcore appearance, as the spikes, chains and billowing cape are all an extension of Leetha and her powers. The suit can also make the wearer blend in with their surroundings.
Leetha's other abilities enhance Spawn by allowing him to glide and even fly. The initially fluid symbiote also has incredible physical strength, making Spawn's superhuman strength even greater when he wears it. There's also its ability to react to danger and protect its user, both through manifesting spikes and other weapons as well as adding to their durability and physical dexterity. This all adds up to make the already incredibly tough Spawn an even tougher customer, and it's all thanks to the suit. Thus, in the case of Al Simmons and other hellspawns, the clothes definitely make the man.