Tales From the Yawning Portal
Garon remembered the last time anyone, aside from Talgen and Sharwyn, asked questions about the Sunless Citadel. About thirteen years ago, a grim human named Belak stopped by, and he had a very large pet frog.
Yusdrayl told the party about Belak calling him “The Outcast”, and saying “he lives below. He grows the fruit, which he gives to the goblins. The dragon-thieving goblins are his servants.”
Erky Timbers talked of Belak as well, saying he had heard the goblins talk about the Twilight Grove down below. A wicked old human called Belak – a spellcaster, he suspected – tend an enchanted garden and harvests fruit from something the goblins call the Gulthias Tree, but they speak of it only in the most terrified of whispers. The enchanted fruit grows on the Gulthias Tree.