Underlord + Grimstroke

Why this works

Locking an enemy down inside a Firestorm is the main idea here. Underlord's Pit of Malice provides a reliable root that allows Grimstroke to easily land a Phantom's Embrace for a follow-up silence or a fully charged Ink Swell. Going the other way, Grimstroke's slows and Soulbind can hold enemies together, setting up a perfect multi-hero Pit. This creates a solid pocket of control and damage that can be effective for securing kills on out-of-position heroes, especially during the laning stage or in mid-game skirmishes around objectives.

The problem is that this setup, while effective, isn't particularly unique or hard to see coming. Both heroes have noticeable cast animations, giving aware enemies a chance to react with defensive items or mobility spells. The combo provides control and sustained damage, but it lacks the instant burst needed to delete a priority target before a fight turns. In the end, Underlord creates a safe frontline for Grimstroke to operate from, but their success together relies more on general teamfight execution than on a specific, game-breaking interaction between their spells.