Note: For all map points of nameds in Miragul's Nightmare (for "miragulmare.txt" map files), see this quest entry.
Soul Taster spawns in the open area in the southernmost part of the zone (around /loc -370, 800). PHs are the "a silent shadow" mobs in this area.
Soul Taster hits for a max ~13,000 and doesn't cast any AEs. As long as it is alive and aggro, however, you'll get timed adds two at a time (1x Soul Taster Spirit + 1x Soul Taster Shadow). These adds each hit for a max ~3,500; have lower than normal hitpoints; and cast "Infernal Combustion" (40' range AE for 32,000 dmg). As these adds are timed, the longer Soul Taster is alive, the more adds you'll get.