Since a lot of time has passed and things have changed I've decided to unveil all (?) the mysteries left in this thread
Solution:
"Steam" stands for the game's Steam id, which is 248570.
"Official Clans" was the part which caused the most confusion. Many people have guessed 44, which is "Official Clans" forum id, or 42 which was the number of clans listed on that subforum, forgetting about the "Russian Clans" subforum "Официальные кланы", which is basically the same thing except in Russian. I didn't include legendary clans because even though they have square brackets they are listed in the "Dead Clans" section. Therefore, the correct number was 49.
"Head Hunter" stood for the Head Hunter achievement id, 21.
"22/11/12" at the bottom of the main forum page you can find this line: "Most users ever online was 14,456, Nov 22, 2012 at 03:43 AM".
"Aether" - Aether clan forum id is 666.
"High Speed" - the record for the highest speed attained in Toribash SP is 75.61, held by pusga.
"[kz]" - clan id of a dead clan Knotz is 100. Notice that the key is written differently from Aether, hence the difference between clan/forum ids.
"Regal" - item id of The Regal, Alpha's Clan League 2014 prize is 2021.
"Sparta" - forum id of a dead organization "Sparta" is 599.

Having that, our equation looks like this:
[((248570 / 49) * 21) / ((14456 + 666) / (75.61 * 100)) + 2021 - (599 + 1)].UT =
[(106530 / (15122 / 7561) + 1421].UT =
[(106530 / 2 + 1421].UT =
[53265 + 1421].UT =
[54686].UT
54686 is Oblivion's user id
I used UT as an abbreviation for User Title, so the correct answer for this riddle was Que outro valor mais alto se alevanta (worth noting that I have no clue what that means).


Solution:
The oldest standing ban on the ban list is Ceviuss (his ban reason says: "Cos you SUCK. Fool."). His user id is the same as this thread's id, made by a second banned person, loje. The difference between their user ids is 20984 - 19351 = 1633. Amber colour description mentions that it's made from fossilized ancients, the item that's often called ring is DQ. Amber DQ item id is 703, if you multiply that by 2 and by 1633 you get 1406 * 1633 = 2295998, which is the user id of this guy (called him a ghost because he's only played one game and disappeared forever. Fifty thousand people used to play this. Now it's a ghost game). In his Deactivated inventory he has an empty set called "Set: Artifact is in this set". Pointing that out would grant you the prize and enable me to continue the storyline, but that never happened. Perhaps the hidden empty set was a little too much.

I am going to open this thread so you can post about how close you were to cracking these. This doesn't mean I will start posting riddles again though. Maybe some time in the future, but no promises.