To see the Slasher, a player must go into Rave vision past scene 10. Then they will be able to see the Slasher. The player must be very careful though, as the Slasher can move quickly, and its chainsaw is very powerful, enough to kill a player in one hit, even with Tuff 'Nuff. The Slasher is also unkillable by any weapon, excluding the Smiley, which can only be acquired after completion of the main quest.
In The Beast from Beyond, Slashers are much more difficult to deal with due to the lack of rave mode which is no longer necessary to have them spawn in. Slashers will not appear til much later than their earliest point in Rave. However, unlike in Rave, the Slasher can be killed here by any weapon.