Dawnbreaker + Magnus

Why this works

Focusing only on the big ultimates misses the point here. The consistent value comes from Magnus granting Empower to Dawnbreaker. This gives her a farming accelerator and cleave damage that works well with her natural desire to be in the middle of fights. When she gets Luminosity procs, the bonus damage and cleave spread that healing and damage around. A well-timed Reverse Polarity can hold enemies in place for a full Starbreaker channel, but the core of the partnership is that Magnus makes Dawnbreaker a stronger right-clicking core at all stages.

This dynamic means Dawnbreaker hits her item timings faster than she normally would. In the mid-game, the enemy team is stretched thin trying to deal with two major threats. Magnus is looking for a multi-hero setup with his Blink Dagger, while an Empowered Dawnbreaker is a split-pushing problem who can instantly join a fight anywhere with Solar Guardian. The enemy has to choose between playing spread out to avoid Reverse Polarity or grouping up to handle a global gank, and either choice leaves them vulnerable to one of these two heroes.