He can definitely make the monster sluggish enough so that the tentacles are definitely slower and even easier to dodge. But with their experience and combined efforts they shouldn't have too much trouble destroying the monster completely. Be warned that even if just one tentacle is left uncut, it will be able to revive itself later, but it will take time so even if they'd miss some they could move on (but by the time they come back there might be a smaller plant tentacle monster).

After taking care of the monster they are set to continue. Not long after it they will encounter a treehouse that seems a little abandoned, but still very much in good shape. Would they like to check it out?