Rubick + Tidehunter

Why this works

Winning a teamfight often hinges on landing a big ultimate, and Tidehunter provides one of the best. The long stun duration from Ravage creates a perfect opportunity for Rubick to reposition safely, survey the enemy's abilities, and take his pick with Spell Steal. It removes the immediate danger he usually faces when trying to get into casting range. Furthermore, Rubick can use Telekinesis to lift a priority target right as the Ravage stun is about to end, extending the lockdown and ensuring they can't immediately retaliate or escape.

This combo creates space across the map after a successful fight. The threat of Ravage forces enemies to spread out, which can make them vulnerable to pickoffs or cede tower control. A support Rubick especially benefits from the gold and safety that come from winning teamfights, allowing him to get the items he needs to position better. The enemy's main counterplay is to try and burst Tidehunter before he can use his ultimate or to bait it out poorly. Since the setup relies on a long cooldown and a specific enemy spell lineup for Rubick, the advantage is noticeable but not overwhelming.