Death Prophet + Viper

Why this works

Applying a full Viper Strike onto a target is often the goal, but Death Prophet wants to do the same thing with Spirit Siphon. Both heroes focus on applying sustained magic damage and slows, leading to a redundant game plan. They don't set each other up well because they are both trying to be the one to kite and drain an enemy. This overlap extends to their damage types, making it very straightforward for opponents to build magic resistance. Instead of creating a new problem for the enemy team, they present the same problem twice, which is much easier to solve.

The strategy becomes very one-dimensional. Both Viper and Death Prophet want to hit their mid-game timing and group up to push towers with Exorcism. This can work from ahead, but the lineup lacks the hard lockdown needed to guarantee kills on mobile heroes. If that initial push fails or the enemy stalls the game, this duo has a very difficult time playing from behind. They don't scale like a traditional late-game core and their lack of stuns makes it hard to adapt if the game doesn't go exactly as planned.