Ok so first evidence Artic has an A and a C in it, he left the b out to not be so obvious. Second off look at this A(bc)rtic and you see clearly. Also He clearly misspelled Arctic as to not raise too much alarm.

Final Proof:

Artic:I am abc

Does Sandbox need any more evidence? Ban this monster.

Hey guys I found more evidence he admitted to everything in the comments here's a copy/paste before he edited it:

Artic:i agree with all evidence shown