Night Stalker + Warlock

Why this works

Catching an enemy at night becomes a bit more threatening with a Warlock on the team. Night Stalker excels at closing the distance and silencing a single hero, but his damage is usually focused on that one target. Warlock can cast Fatal Bonds on the enemy group before Night Stalker attacks, causing some of that focused burst to spread to linked heroes. It's a way to soften up the whole enemy team during what would normally be a solo pickoff attempt. Warlock's Upheaval can also extend the lockdown, providing a potent slow after Night Stalker's initial silence wears off and making it harder for allies to come to the rescue.

The effectiveness of this duo hinges on them playing together during Night Stalker's timings. A successful gank can be followed up by Warlock's sustain or teamfight spells to secure an objective. A fight initiated by Night Stalker's Dark Ascension provides a good window for Warlock to use Chaotic Offering. However, their game plans can sometimes diverge. If Night Stalker is hunting for solo kills while Warlock is positioned for a defensive five-man fight, their kits don't really augment each other. The synergy requires some deliberate coordination to pay off.