Grell and Colletta send Travis Morgan to Wizard's World in Warlord 34 (June 1980).
The dwarves in the village that Travis Morgan wound up in in the previous issue show him an ancient sword. It has a spot in the hilt for a mystic gem, which looks to be the same shape as the pieces of green gemstone that he has been carrying around for a while now. As he and Shkira deal with the sword, the bottom of the pages show Machiste and Mariah Romanova accompanying Mongo Ironhand to a more powerful wizard, in hopes he can send the two back home.
When Morgan puts the gemstone into the sword it transports him back in time, and he winds up in the same chamber as his old friends. Wralf the Wretched, the more powerful wizard Mongo had brought them to, also is the owner of the sword, though in his own era. He wants Morgan's version as well, and magically makes the hero look like a monster, so that his own friends will kill him. Mongo reverses that spell quickly.
Wralf then battles Morgan himself, both using different temporal versions of the same sword. Morgan defeats Wralf, and in doing so shatters the gemstone, in a tidy ouroboric loop.
Mongo explains that Morgan can return home simply by wanting the sword to bring him there, but will not be able to transport Machiste and Mariah. The pair don't seem to mind, though, they are enjoying Wizard World.
Machiste and Mariah return a few months down the road in a Wizard World back-up.