All allied races can make sense if you can work out a story behind them. It doesn’t have to be a complex story.
Start with a simple concept. Look to what races you find appealing and build off from it.
Fun concepts I can suggest:
A Lightforged that attempts to use the Light again, even though it burns their form and could destroy them.
A Highmountain of the Skyhorn tribe that now seeks to the be the master of the sky, even in death.
A Nightborne that twists magic of their foes against them, becoming a proficient mage hunter.
A mechagnome who died and who’s mechanical body is the only thing that is keeping them falling fully apart.
There are many ways to go about it.
I recommend hitting up the Ebon Onslaught as well for role-play!