Mordenkainen's Lost Notebook
9-level Transmutation
You choose a target within range and ritually transform it into an oak tree. For the duration, that oak tree animates as a treant (though it can’t animate trees) and serves as you command. You either command it to follow and protect you or leave it somewhere as a guardian. When the spell’s duration expires, the subject becomes in all respects a normal oak tree, taking root where it stands. At the beginning of the ritual, the target can make a Constitution saving throw. If it succeeds, while the ritual is in progress it is affected as though by a slow spell, and at the end of the ritual, it returns to normal.