Camelot Park - S2.E6

During a battle too early to tell which side is winning, the Warlords abruptly retreat when a lunar eclipse begins. Merlin remembers too late that it has transported the three attained Keys of Truth through an unspecified time in the twentieth century, which Morgana has told the Warlords. The portal is Grinlap's tree, so Arthur, Darren, and Tone return to time-travel again and reclaim the keys, but the Warlords are ahead of them. Annoyed by their confrontation in his home, Grinlap watches the Warlords go through the portal then throws the knights in.