Per 
Special Containment Procedures: The building in which SCP-4286 resides has been purchased by the Foundation and transformed into Containment Site-504, also built to contain SCP-4511. As nobody has ever come out of SCP-4286 alive, any test subjects are to be transported to Containment Site-504’s Scientific Department and be asked questions about their time inside SCP-4286. Should SCP-4286-A be found outside the interior of SCP-4286, it is to be terminated.
Description: SCP-4286 is a totally safe and normal elevator that just begs to be ridden.
SCP-4286 is a standard elevator that appears to be manufactured by Dover Elevators Company, although its actual manufacturer is currently unknown. When a subject enters SCP-4286, they will be locked inside of SCP-4286’s interior, before being murdered by a black humanoid entity of unknown origin classified SCP-4286-A. The system that allows SCP-4286-A to only reveal itself when a subject has been fully contained within SCP-4286 is currently unknown but it would be awesome to find out for yourself.
Addendum 4286-1:
Dr. [REDACTED]: D-23834, enter SCP-4286.
D-23834: Roger that, Dr. [REDACTED]. *enters 4286’s interior*
*door locking D-23834 in*
SCP-4286-A: WHAT ARE YOU DOING IN MY ELEVATOR!?!? NOW YOU CAN DIE!!!
D-23834: No! *pries door open* *runs out of 4286*
SCP-4286-A: *runs after D-23834* NOW DIE!!!
Security Department: *fires gun at 4286-A*
SCP-4286-A: NOOOOOOOO!!! I HAVE BEEN DEFEATED!!! *flops to the ground*
D-23834: Whew. If it weren’t for those security personnel, I would have been 4286-A’s dinner!