Random Attacks

Easy, in the missile create a a_jump with the name of the attacks, here one of my monsters

between further down is the a_jump means that would be less probable to do being the most common here the IMP and the least common the Baron

        Missile:
                TNT1 A 0 A_Jump(128,"Imp")
                TNT1 A 0 A_Jump(128,"Boun", "Seeker")
                TNT1 A 0 A_Jump(128,"Baron")
                Goto See
        Imp:
                IMP3 A 20 Bright A_FaceTarget
                IMP3 AB 2 Bright 
                TROO G 2 Bright A_CustomMissile("DoomImpBall", 40, 0, random(-3, 3), 0)
                TROO G 1 Bright A_SpidRefire
                Goto Imp+1
        Boun:
                IMP3 A 8 A_FaceTarget
                IMP3 B 8 A_FaceTarget
                TROO G 1 BRIGHT A_CustomMissile("BouncingBall", 40, 0, random(-16, 16), 0)
                Goto See
        Baron:
                IMP3 A 8 A_FaceTarget
               IMP3 B 8 A_FaceTarget
               TROO G 8 A_BruisAttack
                Goto See
        Seeker:
                IMP3 A 8 A_FaceTarget
                IMP3 B 8 A_FaceTarget
                TROO GGG 0 BRIGHT A_CustomMissile("SoulHarvesterBall", 40, 0, random(-16, 16), 0)
                TROO G 8
                Goto See

For more information: https://zdoom.org/wiki/A_Jump