There are at least 6 bands of this name: 1) Avenger is a Czech black/death band from Volyně (Czech Republic) formed in 1992 by Petr Rámus Mecák. They were formerly known as Astaroth and currently have a side-project called Black Rain. They released 2 demos (Minster Of Madness; The Black Zone), 4 full length albums (Shadows Of The Damned (1998); Fall Of Devotion, Wrath and Blasphemy(1999); Godless(2003);Feast of Anger - Joy of Despair(2009)), one compilation (Minster Of Madness/The Black Zone(2009), and one live album (Live at Open Hell Fest 2003).
There are 3 bands that share the name Mammoth and one band formerly known as Mammoth: (UK) 1. After the split of Gillan in 1982, the bearded John McCoy (bass guitar; 19 stone) recruited session musicians 'Tubby' Vinnie Reed (drums; 22 stone), 'Big' Mac Baker (guitars; 24 stone) and Nicky Moore (vocals; 20 stone and 5'6") for his solo project.
Initially christened 'Dinosaur', they changed their names after complaints from a similarly titled California blues outfit.