HOME is a spell word engraved on the Amulet found on Enchanted Island.
Background[]
The spell causes the user to return to home of the caster, or home of someone near the caster to their native homeland.
After convincing Valanice to marry him, Graham used the spell to return to the Land of Kolyma ('western Kolyma', Valanice's home) where they were married in the chapel of the monastery in her homeland.
Had Graham used it without Valanice, he would have returned directly to Daventry, his native homeland.
Perhaps its somewhat peculiar that the amulet brought Valanice to western Kolyma when her parents castle is in the east beyond the Forest Mountain. Or even possibly brought to the monastery. Was she cloistered there perhaps taught by the monks?
Behind the scenes[]
Perhaps alternatively the Official Book of King's Quest may imply that Graham was brought home to Daventry by using the Amulet and it was there that they got married in a chapel similar to the one he visited in Kolyma. Similar to the account in the KQ5 Hintbook: The World of King's Quest: A Brief History of Daventry and Once Upon a Time in a Land Faraway.
In an alternate ending, if you use the Amulet before rescuing Valanice, Graham will be teleported back to Castle Daventry and a message will comment on how sad it is that Graham returned home without a bride.