Trevor is the boss in the mission called "Trevor and the Phone booth" in Episode 3 of Survival Crisis Z
According your commander, there is a phone booth inside a building that its ringing. When somebody answers, Trevor asks if them won't come to see his "beauty" and simply vanish.
After reaching the phone and listening to Trevor to come and see his "beauty", the outside and its surroundings become the Hell Dimension.
According to the dialogue he used to be a survivor and that a "tall man" took care of him (probably before Trevor died) and showed a beauty "he could never understand" and he offers the player to show his beauty.
His head becomes 8 tentacles and he starts running towards you like a normal infected (similar to Mark's transformation). He can appear anywhere inside the building he is and when he dies, he explodes.
This battle is similar to Mark's. Normally, the battle is fought alone, however, if the infected appear, first take care of them. Then keep moving and be aware that Trevor can dissapear and apper anywhere the building. Bring with you as many medkits or healing items as you can find, a fast-shooting weapon or medium range weapon is also a good choice (SMG, handgun with Pistol God skill, handcannon, Tec-9 are good choices). Explosive might not be a good idea as he moves constantly and disappears