Crystal Maiden + Grimstroke

Why this works

Landing a Soulbind on two enemies creates the ideal setup for Crystal Maiden. Her Frostbite, a single-target root, will be duplicated and lock down both tethered heroes for its full, long duration. This is an incredible amount of control coming from two supports, often ensuring a kill if a core is nearby to deal damage. Grimstroke can even use Stroke of Fate to slow targets first, making it easier to land the initial Soulbind. Once the roots are on, Maiden can follow up with Crystal Nova to pile on more slow and damage, making escape almost impossible.

The game plan is to play aggressively once Grimstroke has his ultimate. Crystal Maiden's Arcane Aura provides the necessary mana regeneration for Grimstroke to constantly pressure lanes and look for openings. In larger fights, catching two heroes with the Soulbind and Frostbite combo can instantly take them out of the fight, allowing your team to focus them down or ignore them to deal with others. The threat forces opponents to position awkwardly far apart, making it harder for them to coordinate their own attacks and spells.