Gruustir tried to copy Pha Rann many times in that one's creation of elves. It is said that the first attempts resulted in kobolds, the second in goblins, and the third with orcs. Not to be outdone, he then tried to improve on them and so spawned hobgoblins, ogres, and eventually trolls. At that point, he gave up.
When Pha Rann pulled Creation into Heaven, Gruustir approached Pha Rann and said, "Behold, all that you taught me and my creations! Let them come to Heaven too." But, as the story goes, Pha Rann deemed them incomplete and so Gruustir refused to ascend and fell instead into the Abyss. It is not known exactly where Gruustir resides though he occasionally rallies to his creations' needs, with overt favoritism shown the Orcs. According to their genesis, Pha Rann almost let the orcs into Heaven, but the elves protested so loudly that Pha Rann changed his mind.
This plays into their racial identity and hatred for elves. It's not that they hate them on a personal level. Rather, they are taught from birth that elves are whiny, holier than thou, and think orcs are ugly. Most encounters serve to reinforce these attitudes.
Meanwhile, Gruustir will occasionally decide to sponsor a chosen orc and raise them up as an avatar to the other races to test and see if things have changed. This is always done as a prelude to war. The chosen orc has the power to command all of Gruustir's creations and so far have chosen all out war. Maybe, in 1800 Dar, RiVule will be different.