Invoker + Viper

Why this works

Putting these two heroes on the same team often creates a resource-heavy draft. Both Invoker and Viper can be greedy, wanting solo lane experience and farm to hit their respective timings. Invoker needs levels for his spells, while a core Viper needs items to become a durable frontline presence. This can sometimes starve the rest of the team and make the lineup inflexible. The main mechanical synergy comes from their single-target control. Viper's slows, especially from Viper Strike, provide an incredibly easy setup for an Invoker to land a full Sun Strike, Meteor, and Deafening Blast combo.

The game plan usually revolves around winning the lanes and then using that advantage to secure pickoffs. With Viper slowing a target to a crawl, Invoker has all the time he needs to connect his abilities from a safe distance. This can be very effective for controlling the map during the mid-game. However, the duo can struggle if they fall behind or if the enemy team starts grouping as five. They can lack the widespread area-of-effect damage and mobility needed for large-scale teamfights, and their combined power is less impressive when they can't isolate a single hero.