Leshrac + Lich

Why this works

Setting up a Split Earth is the main idea here. Lich can use Sinister Gaze to force an enemy hero to walk toward him, creating a predictable path for Leshrac to land his stun. Following that up with slows from both heroes can secure a kill. Later on, Lich can put a Frost Shield on a diving Leshrac, making him much more durable as he runs into the enemy team with Pulse Nova active. This gives Leshrac a bit more room to operate and output his damage without being immediately focused and killed.

The plan is straightforward but requires good coordination. If Lich pulls an enemy away from Leshrac, the whole setup fails. Both heroes are also quite vulnerable to being jumped on, as neither has a reliable escape mechanism. Enemies will often try to split them up or burst one of them down before they can execute their combo. While the synergy exists on paper, in a real game it's often too slow or awkward to pull off consistently against opponents who know how to play around it, leading to a fairly neutral outcome.