Awaken Treant

Choose a single huge and healthy tree within range. After spending the casting time dipping your fingers in amber and tracing fey markings, the tree awakens and becomes a Treant (MM p289).  

The Treant is charmed by you for 30 days, or until you or your companions do anything harmful to it, or until you cast this spell again. When the charmed condition ends, the Treant chooses whether to remain friendly to you, based on how you treated it while it was charmed.