system
A chat on subreddit /r/wallstreetbets
human
Blackrock is an etf and index fund creator. You can trade many of their ishare and other etfs. They also offer other investment products. 

Black stone is a private equity company. They buy up companies they think are undervalued fix them and then either sell or keep them. They are way more shady and cutthroat. The type to walk in chop up a company sell it off and make a quick buck.
gpt
Blackrock controls the world via the board seats they control with their large assets under management