Black Widow - Sacrifice (1970)

An underground classic of British occult prog. If you like Hammond organ, saxophone, noodle-y solos, and Satan, you've come to the right place. 

Track listing:

1. In Ancient Days

2. Way to Power

3. Come to the Sabbat

4. Conjuration

5. Seduction

6. Attack of the Demon

7. Sacrifice

Come, come, come to the Sabbat

Come to the Sabbat

Satan's there!

You should also hear:

Aum - Resurrection (1969)

Horrific Child - L'Étrange Mr Winster (1976)