Oppon is the shared name for a pair of twin Ascendants (the Malazan universe's gods); we never learn their individual names.
The people of the Malazan world don't always identify the twins as separate people. Rather, they consider them to be two parts of the same entity, reflecting two "sides of a coin" (a metaphor which Oppon takes rather literally). Any time someone in the novels identifies Oppon by name, they almost always mean both twins.
(This actually fits very well with their behavior: on those rare occasions where the twins make an on-screen appearance, they are also cooperating with each other and working in tandem, acting as a single force.)
Whenever there was a distinction made between them, the only names they were ever given were Lord and Lady of Chance. They are also sometimes identified as "the male/brother" and "the female/sister". Their intervention in the world is also often described in terms of pushing and pulling (e.g. counterbalancing each other). In general, when someone was having bad luck, it was attributed to the Lord "pushing" luck away from them, while good luck was attributed to the Lady "pulling" luck towards them.
You're probably not far enough to really "understand" the Deck of Dragons (mostly because no one alive "understands" the Deck of Dragons), but as far as I can remember, Oppon was unaligned in the Deck, meaning they weren't part of one of the larger House structures, and thus didn't really have a "boss".
Very late in the series (Dust of Dreams, according to the Malazan wiki, though things in this series tend to blur together in my head) you will learn a bit more about them and where their Ascendant nature derives from:
They are the twin children of the Forkrul Asail Ascendant called Sechul Lath and the grandchildren of the Elder Goddess Kilmandaros, both of whom are tied to the power of Chance and Luck.