Phantom Lancer + Skywrath Mage

Why this works

Catching someone out of position becomes incredibly lethal. Phantom Lancer provides the initial setup with a Spirit Lance slow, which is all Skywrath Mage needs to land his entire combo. The target gets silenced by Ancient Seal, then obliterated by Mystic Flare before they can use defensive spells or items. This shores up one of Phantom Lancer's biggest needs: reliable burst damage to secure kills before his illusions can fully swarm a target. Skywrath essentially guarantees that any hero PL manages to slow is a dead hero, which lets him snowball much faster.

This pattern starts in the lane, where the constant threat of a slow into massive magic damage makes it very difficult to contest Phantom Lancer's farm. Into the mid-game, the duo roams for pickoffs, creating space and accelerating PL towards his critical items. The enemy's main counterplay is to group up, making it harder to find isolated targets. They have to avoid fighting alone and try to turn on the fragile Skywrath Mage after he commits his spells. The game becomes a race for PL to get too big to stop before the enemy team can effectively teamfight as five.