Flame Pernix is one of the bosses that can drain your prayer "Soulspit". Flame Pernix has a combat level of 420 and can do some damage. But don't worry this boss won't attack you unless you attack it first. This boss might be challenging for new players but not impossible.
You can find Flame Pernix by using the Boss Teleport System.
The best way to kill this boss is by using prayer "Soulspit" (Level 92 recommended) since this boss drain payer "Soulspit", its best to bring food (Rocktail or Shark) and some prayer potions. Some good armor to use would be Flame Torva , American Torva, Dragonbone (U), or higher/better armor. Your also going to need a fast hitting weapon, such as a Glock, or Ice katana, or an Assault rifle.