The form of Omega Super Saiyan can only be obtained by first mastering the forms of Super Saiyan 1-10, 11-15 are not required unless you really need them. Once the ten forms are mastered, you must be granted permisson to enter the demension of The Chosen Warriors, which were chosen by the creator of the multiverse, Ulronaty. Once there you must find a man called the Combinist, he can combine any material and or power into one. Once you meet him, give him your request and he will literally rip your Super Saiyan forms right out of you, and combine them all into a massive form called the Omega Super Saiyan (Named by Rythian) This form will make you into a God, your base power level is times by 5 Billion (All depends on how many years of training you have, Rythian has about twenty thousand so his multiplier is 17 Billion).
While in this form great caution is advices, just a single move of a muscle will destroy the land around you, this form is only for fighting in a blank universe, where there is nothingness. (Universe 20) The only one to ever obtain this form is Rythian Alhizen, a character from an alternate Dragon Ball universe.
The users hair becomes a greenish-white, no aura or lightning surrounds you, the form is so powerful that it executes the presents of the aura and lighting.