Thunderhead Keep deems its own term in this Terminology Guide. It is, hands
down, the most frequently talked about mission and the mission that most
people complain about. Thunderhead Keep is so hard to people, that it has
been deemed the “Noob Filter” of the game to keep people from progessing
to the Ring of Fire Island Chains. You will find Thunderhead Keep as the last
mission in the Southern Shiverpeaks areas.

EXAMPLE: Thunderhead Keep is so hard that it can blow me.