Grimstroke + Luna

Why this works

Thinking Luna's Eclipse will get duplicated by Soulbind is a common trap. Grimstroke's ultimate only copies single-target spells, and Eclipse is an area-of-effect ability that hits random enemies. It won't focus down the bound targets. The actual synergy here is with Luna's Lucent Beam. When Grimstroke lands Soulbind on two heroes, a single cast of Lucent Beam will hit them both, providing a strong burst of magical damage and a mini-stun. This turns a single-target nuke into a potent tool for locking down and damaging two enemies at once, which can be particularly effective during the laning stage or for ganks.

In a real game, this pairing gives you solid pickoff potential. Finding two heroes with Soulbind and following up with the double Lucent Beam can secure a crucial kill before a fight even begins. Beyond that specific interaction, however, their kits don't overlap much. Luna still has to play her game, farming up to deal massive physical damage with Moon Glaives in teamfights, while Grimstroke provides more general disruption with slows and silences. They function well together as individual heroes, but don't fundamentally enable a unique strategy, making their overall performance fairly predictable.