The Hoarding Merregon can initially be found taking part in Yurgir's ambush. If Yurgir has been pacified, it lounges beside a campfire at X: -664 Y: -760.
Using Detect Thoughts on it, reveals that it has slightly more self-will than other Merregons and that its driving purpose is to keep feeding the Displacer Beast and protect and grow Yurgir's stock. The party can then tell the Merregon that they are tending the Displacer Beast now, which makes the Merregon give them five Merregon Potions which can be thrown to befuddle the enemy.