Yes, you need a guide for Indrahaar Pass.
Reasons as follows :-
1). Indrahaar is not done by many , so the trail is not well marked.
2). The trail consists of Big rocks and Boulders which make the way very tough and if you follow the wrong trail you might end up to other place.
3). There are 3 summit at the top, Camel peak, Indrahaar pass, Moon peak and the trail is same for all, and the shepherds or guide knows the exact trail.
4). I have seen people doing the trek in late night, which have cost there life in danger, and the guide knows the weather conditions, because being a local they can predict better.
5). The weather will change in seconds, so if the trail is not visible, you might end up lost in different directions.
That sum ups the all points.
If you still want to go Solo, then plan to reach Indrahaar by 11:30 A:M, because after that the weather is not good.
In my case, the clouds were blocking the way and there was continuous rain, when I was descending it.
So it’s a tough trek overall and if you want to listen your heartbeat, then try it once, last 300 meters will be very tough, being stairs.
If you want any assistance in terms of guide, let me know, I will let you know the cheapest guide for Indrahaar.
Have a safe trek.
Thanks !!