Outrage of the Ancients (LitRPG Apocalypse)

They say the king will return during his country’s greatest hour of need. They never say what happens when they all do.  All of humanity received the same warning, about seven magical challenges that it will have to survive or go extinct, but modern man must not face this threat alone. Arthur Pendragon emerges from beneath Glastonbury Tor, Francis Drake fulfills his ancient oath to serve his nation beyond death, and in Ulaanbaatar, Genghis Khan rules once again. However, there are others still, throwing an already chaotic world further out of whack. Can humanity stabilize itself and continue on when even the very world itself seems to have turned against them, only having ancient legends to rely on?