K'ril Tsutsaroth is within God Wars Dungeon, and it is recommended to at least have Trollheim Teleport (Lunar) unlocked. You can also use God wars teleport or a Max Guild boss portal tuned to K'ril Tsutsaroth. From Trollheim, climb down the cliffsides go north past the thrower trolls, past the large rock, and down the entrance into the dungeon near the wolves. Once there, run north and cross the river into Zamorak's Fortress - this requires 70 Constitution, which is not boostable. This will drain your prayer points to 0.