Fablehaven (1970)

When Kendra and Seth Sorenson visit their grandpa's mansion and gated grounds, they soon discover that the estate secretly houses magical creatures including fairies, goblins, and witches. They must learn how to use magic to keep Fablehaven safe. When their grandfather is kidnapped by goblins, the siblings embark on a journey to rescue him as a witch named Muriel plots the release of a powerful demon named Bahamut, which could result in the end of the world.