It's a tale concerning SCP-603 and WAN (Broken God, Church of Maxwellism's version). The gif is created by Fantem who is awesome and helped me a lot on this.
Thanks for those who helped me in the forum! Special thanks to ashausesall who translated SCP-603 into Chinese or I wouldn't have wrote it in the first place.
(In case anyone's interested, here's the Original Chinese version of the tale that may receive an update in the future: http://scpfoundation.123ubb.com/t5241-topic)