Pyro is an Utility Mod developed by ionar2 and some others. It is often referred to as a SalHack skid, due to some similarities and same developer.
Pyro is/was known for AutoDupe and AutoCrystal, which are/were great features of the client. Pyro also stars some amazing visuals - including SuperheroFX. All other modules in the render category are very customizable and they work well.
Most powerful combat/movement modules are AutoCrystal, Longjump, CityBoss, AutoTrap and Surround. They feature lots of customizability even though they are rather simple to use. With a good configuration, they can/will be very powerful in combat.
Pyro's GUI looks rather nice when you modify it to your personal liking. Personally, I prefer the GUI of RusherHack more than Pyro.
Pyro is not currently a recommendable client due to performance issues and lack of updates. Version 1.4.1 is very laggy. If you are going to purchase it, wait for 1.5 to come out.
The support in the Pyro Discord is handled mainly by other users of the client instead of the support team.
Conclusion: Good looking client with decent modules overall, but simply not worth 20$. The slow updates and performance issues even on decent specs is a huge con. If you want Pyro, you should wait for an update fixing the broken modules and performance issues before buying the client.