I still believe Limbo is one of Madara's MS abilities which was boosted with Rinnegan as it is filled with Rikudou chakra making it more durable and senseable only with Rikudou Senjutsu and watchable only by Rinnegan so:
First ability: Invisible clone, senseable with Sage mode(Hashirama had counter for this), watchable with Doujutsu(or just sharingan)
Second ability: Seeing through all kind of clones and able to differ original from rest of clones.
However, Obito has 3 abilities if we count phasing ability as well then we have: Long wrap, close wrap and phasing so
Invisible clone, ability to seeing and differ original from rest of any kind of clones, ? Maybe invisible clone for each eye, while each eye have passive ability to see through clones...
I hope I helped
