Thor #253 Nov 1976
"Chaos in the Kingdom of the Trolls"
Ulik, thinking Thor dead, goes to attack the dragon;
Ulik defeats it and takes its eye, only to find Thor standing in his path;

Thor manages to get the ruby from Ulik;

Ulik tells Thor why he needs the ruby; The Trolls have accidentally dug through to another dimension,
where lives the bestial Trogg; Trogg killed many trolls before they could seal the portal, but they need
the ruby to seal it permanently; Thor agrees to help Ulik defeat Trogg if he can keep the ruby.

Script by Len Wein, pencils by John Buscema (breakdowns) and Tony Dezuniga (finished art), inks by Tony Dezuniga