Altar is a collaborative album by Japanese experimental music group Boris and American drone metal band Sunn O))), released on October 31, 2006, through Southern Lord Records (SUNN62). A limited two-CD edition was released on October 23 via Southern Lord with a 28-minute bonus track with Sunn O))), Boris, and Dylan Carlson, titled "Her Lips Were Wet with Venom". Inoxia Records released their own two-CD version in 2006 which features a bonus track on the first disc, "The Sinking Belle ", and also features "Her Lips Were Wet with Venom" on disc 2.