An intruder in a dream usually reflects boundaries that feel violated -- a sense that your space, privacy, or safety has been compromised somewhere in waking life. The vulnerability in these dreams is often the real message, more than the intruder's identity. If you're able to face or remove the intruder, the dream may be showing you a boundary you're finally ready to defend.
A Planet in an Angle doth more effectually produce his effects, but remiss in Cadent Houses. - William Lilly (1602.-1681.)