My new SCP is the anomaly that… destroyed the Mayans.
Here is what happened, the Mayans were eradicated by an SCP that was hiding within one of their temples. The SCP is a black mist with a humanoid form. The humanoid has bright white eyes and mouth, and is always grinning. This creature whispers into the minds of its victims, making them fall asleep. It then opens its mouth, and inhales their entire being, clothing and all.
The temple itself is also an anomaly. It appears for only a week and every night the anomaly leaves the temple and hunts for victims if none are near. The foundation learned of this after discovering the sudden appearance of a temple at the location of a huge forest clearing. They then sent an MTF to investigate it and within it they discovered the anomaly.
Also the date that the anomaly first appeared was December 21, 2012. The Mayans knew that this was the date when the temple would reappear and possible destroy all of civilization.
Please tell me if this idea interests you and how this could be improved in any way.