Death Takes a Halliwell - S3-E16
Corrected entry: Unless someone else cleared out Cole's apartment, Cole/Belthazor would have been careful and smart enough not to leave behind the altar for exactly what happens in this episode.
Death Takes a Halliwell - S3-E16
Corrected entry: When the police inspector comes to the manor to ask Phoebe what she knows about Cole's disappearance, he says that the landlady was found with two puncture wounds in her head, but the demon bit her neck, not her head.
Correction: It is never stated that Cole cleared out the apartment he wouldn't have had time to do such a thing or even cared enough. I doubt the landlord would've discovered the alter it was hidden.