SCP-682

 - Hard-to-Destroy Reptile is a Keter-class SCP from Series I, originally created by Dr Gears. SCP-682 is one of the most iconic and popular SCP monsters, due to being frequently cross-referenced with many other SCPs and Tales; as of 2021, it ranks as #8 on the SCP Wiki's list of highest rated pages.

SCP-682 (also known by its official nickname, the "Hard-to-Destroy Reptile"; sometimes simply called "The Reptile" or "The Lizard") is a large, sapient creature with a vaguely reptilian appearance and coming from unknown origins. SCP-682 is highly intelligent, and possesses a violent hatred for all other living beings (with the odd exception of SCP-053), actively trying to kill anyone or anything else it encounters. The Reptile earned its "Hard-to-Destroy" moniker, because it is effectively immortal and extremely difficult (if not outright impossible) to permanently kill it. Aside from being able to regenerate from any physical injuries no matter how severe the damage is, the Reptile also has incredible adaptive abilities; it can temporarily change its body or gain new powers in order to defend or counter whatever form of attack is used against it.

SCP-682 has proven to be a very costly challenge for the SCP Foundation to keep contained, as it frequently escapes from its green acid-filled containment chamber to go on destructive rampages, often resulting in multiple personnel being killed every time. Because of the extreme danger it poses, the Foundation initiated an ongoing program to try and terminate SCP-682 for good, but without any success. On a regular basis, the Foundation tests out various methods of killing, incapacitating, or otherwise neutralizing the Hard-to-Destroy Reptile; usually by exposing it to other highly deadly SCPs, which often backfires in disastrous or unexpected ways. For example,

Termination attempts of SCP-682
SCP-999 was used in an attempt to find out about SCP-682, which ended up in 682 laughing and causing a major containment breach. One stated “While the test was unsuccessful and ended in tragedy, that had to be the funniest thing I have ever seen. I never thought I’d see the day when I would regard SCP-682 as “cute”. Please send me a copy of the security tapes ASAP.”

SCP-409 was used to attempt to crystallize the Reptile. He experienced trauma and was in extreme pain. 682 was 62% crystallized when the crystals exploded, scattering bits of 409 everywhere. He later recovered even after loss of limbs and organs.