Tyrone
Tyrone is a made-up figure within the Larsonverse. He is also one of the most influential fake characters to Daniel Larson.
Tyrone is supposedly Grace VanderWaal's bodyguard, but is actually a manifestation of an intimidating figure created by trolls.
Meaning to Daniel
The reason Tyrone is worth mentioning is because Daniel is extremely afraid of Tyrone and what he may do to Daniel. One of Daniel's first "encounters" with Tyrone was during the August 29th Meltdown, in which a fake Grace VanderWaal states to Daniel that she will have Tyrone kill him- by butt-fucking Daniel to death. This would be one of the factors that would lead to the incident.
Background
Because Tyrone is not a real person, we really don't have too much information on him. He is a made-up bodyguard of Grace, and is hell-bent on destroying Daniel on Grace's orders.