The Neutron Knights (comic story)

Summary
The TARDIS is summoned to a great castle where the last defenders of Earth are attempting to prevent the vicious Catavolcus and his army from seizing control of the Dragon, a powerful nuclear reactor. An elderly wizard, who claims to have been summoned from another time to aid in Earth’s last battle, also claims to have channelled a greater power to summon the Doctor to this place and time. Before the Doctor can stop him, the wizard sets the reactor to overload, explaining that the defenders can now escape in the TARDIS. Catavolcus’ army storms the castle, and the leader of the defenders gives his life to hold him off while the others escape. As the TARDIS departs, the Dragon explodes, wiping out Catavolcus’ army. The Doctor recovers in a distant forest some time later, near the empty TARDIS, with no memory of his escape -- knowing only that the wizard and his king referred to each other as “Merlin” and “Arthur”. As he prepares to depart, Merlin appears to him in a vision and tells him that they will meet again.

Characters

 * Fourth Doctor

Continuity
to be added