The Undergrowth (Leafeon) in The Obsidian Oath

None of the other members do well into Take Heart aside from Sylveon, but even Sylveon can still be overwhelmed with enough boosts. Therefore, Leafeon's primary role is to ensure the team doesn't instantly lose to Take Heart. Aside from that, it just annoys stuff with Prankster and status conditions and can trade with Destiny Bond if it needs to take out an otherwise out-of-control or unbeatable threat for the team.