Speak with Eitharbor (NPC) at ( -357, -28, -560 ) /waypoint -357, -28, -560 in the Nursery area of Greater Faydark by climbing a tree at the Southern end of the beach.
He casts a spell on you, Safe Passage, that he tells you will grant total invisibility so long as you do not cast or attack. It also suspends movement buffs. It is NOT actually total invisibility. Some creatures see through it (certain aviaks and kobolds outside Kaladim for example) and it will break if you are attacked or if you fall and get hurt. You can still complete this part of the quest even if you no longer have Eitharbor's invis. The spell will take effect the moment you zone into Butcherblock Mountains Leave and re-enter zone to re-cast spell if lost.