Serverblight

The Serverblight has no confirmed true form; instead, it takes on the forms of various Mercenaries it has assimilated. The Serverblight's influence causes the assimilated Mercs to have longer limbs, fingers, and feet, extra body parts, and results in assimilated Mercs no-clipping into each other. It speaks either through voice commands of each Mercenary it has assimilated, by repeating text phrases sent by non-blighted players, or through voice chat by imitating the speech it has heard. Its mimicked voices are commonly deep-pitched, with the exception of seemingly normal-sounding voice chat speech used to coax non-blighted players into traps, as seen in SERVERBLIGHT, where the blighted hector0n uses parts of the real hector0n’s voice chat speech to try to fool dicksalot. It is also shown that once the mimic starts to reveal its identity, the normal speech becomes distorted and low-pitched.

In the case of the Blighted, they often pretend to be normal players to trick others, then shift into a more hostile form where their hands and fingers elongate, and an extra hand emerges from their mouths. It is also shown that the Blighted can grow extra body parts just like the Serverblight, with some being almost unnoticeable unless examined closely; one of the most reported extra extremities witnessed on infected players is a sixth finger on the left hand, seen on the infected forms of both a Heavy and a Scout.

Appearance: It mimics your friends and teammates so it’s a distorted version of charscters

You join a tf2 server because your friend told you to hop on but it wasn’t your friend it was an entity that mimics your friends and other teammates and now your running for your life due to being physically transported into the game and your character being blighted and you find out the name of this monstrosity it’s called the Serverblight.