Merlin can't prevent Arthur considering the surprise appearance of a unicorn as a trophy during a hunt. Uther is proud of the catch, but the legend Gaius fears comes true: killing a unicorn unleashes a curse (in this case, starvation for all Camelot). Immediately, all edible crops die and drinking water turns into sand. Arthur's disbelief is hard to overcome, even after an appearance from Anhora, the old magical keeper of unicorns, whose tests are Arthut's only hope to lift the curse. After passing the first inadvertently and seeing the water returned, Arthur is willing, but fails the second hot-headedly. Seeking Anhora, Merlin learns the last and decisive test is in the labyrinth of Gedreff. He braves Arthur's order not to follow, which proves necessary for the test to happen.
—KGF Vissers