So, obviously this is a Chaos support (though you could easily tell that from the name). I'll try and fix the OCG a little.
"1 LIGHT monster + 1 DARK monster
The Fusion Materials used to Fusion Summon this card must have different Levels. Cannot be destroyed by battle with a FIRE, EARTH, WIND, WATER or DIVINE monster. If you control a monster whose Special Summoning conditions require banishing 1 LIGHT monster and 1 DARK monster from your Graveyard, this card cannot be targeted by card effects. During your turn, you can send this card you control to the Graveyard; Special Summon one Level 8 LIGHT or DARK monster from your Main Deck, ignoring its Summoning conditions."
As a Chaos support, I can't see this being used for anything other than getting a BLS, as there's no other real Chaos monsters you'd really be using that satisfy the requirement. If you've already summoned your BLS and haven't got it back into your main deck, this card is pretty much dead. However, if you've got your BLS in your deck, I'd still say that the only way this trumps actually having a BLS and fulfilling its summoning condition is if you don't have a BLS in your hand, but then you'd have to count on having a Polymerisation/Fusion Gate in your hand or on the field, which isn't really beneficial to Chaos. If you had Chaos Sorcerer on the field already whilst your opponent controls one monster, then summoned this and got BLS out, then used the two monsters you put in the graveyard to summon this to summon another Chaos Sorcerer, that's 5300 points of damage for practically no cost at all apart from hand advantage, but then again that's being put to incredibly efficient use. I doubt that you'd keep this on the field long enough for it to be battled, if I'm honest. I do like that you've limited it to main deck, because nobody likes a free Beelze/Mefist. However, you need to slam a cost and/or a Once Per Turn clause on this, because Call of the Haunted, etc. is a thing.
Otherwise, I do like that you've thought hard about a competitive Chaos support, I'd just appreciate some consideration about making it balanced. Also, I don't really see how the picture and name go together, but that's just me being persnickety.
+ Definitely competitive (IMO)
+ Limiting it to Main Deck means you're not taking the mick with which monsters you're summoning
- Pretty broken; try to add a cost and/or a OPT