So there is a lot to cover, but because i am a genius, i thought of breaking it into sections, so there are now three sections. Number 1 why is my commander is Bolas and how he works with rest of the deck. Number 2 what the combos are and how they work ( by the way some of these combos were adapted to fit grixis colors ).
Number 3 what you should do in game play with this deck.
Number 1
So my first idea for my commander was actually Thraximundar. Because he is a 6/6 hastey with face eating powers. But he did not have something Bolas does. Thraxy can agro an opponent like hell. However, Bolas can more easily draw out the game by forcing them to discard there hand. That is what you need to win, force your opponent(s) have limited to no resources to fight back and work with.
Number 2
There are about 6 combos in this deck, but most of them have extensions on the building blocks so there are more options.
Combo 1
Self mill/ Chaingun
This is pretty easy, you play Niv-Mizzet and enchant it with a curiosity, now play a lab maniac. Next tap Niv-Mizzet to draw a card, curiosity deals one damage to an opponent, which lets you draw another card. Chaingun your opponent equal to the number of cards in your library, then mill out and lab maniac wins you the game.
Combo 2
Infinite of any color mana/ Self mill
This one in my opinion is awesome. So you play a grim monolith or basalt monolith either works. Next enchant the of them in play with a power artifact. So, say i had grim monolith in play and enchanted it with a power artifact instead of tapping for 3 and untapping for 4, it taps for 3 and untaps for 2. Since it does not untap during your untap step you can untap/ tap during your main. Do this as many times as would like, getting infinite colorless mana. You can just stop there and blightsteel colossus, but i went farther. Now put all your colorless mana into an astral cornucopia. Since it is an artifact it can be tapped right off the bat for any color equal to the number of charge counters on it. You put infinite charge counters on it when you played it, it taps for infinite of any color of mana ( you can only use grixis though)!!! Also if you want or just happen to have banefire using red mana and burn your opponent. Next tap it for blue and play either lab maniac or fate unraveler. Now tap the rest of the mana for either a blue's zenith or a stroke of genius. If you played a lab maniac draw out your library and win. If you played fate unraveler, make your opponent draw out their library and take damage equal to the number of cards they drew.
Combo 3
Self mill
I know you are probably getting bored right now with self mill, so i promise this is the last one. This combo takes a while to get because mana, but it is still amazing. Play omniscience, and then cast enter the infinite. You draw out your library and put one card from your hand into play. If you have not cast omniscience you should do that then, if you have play lab maniac. Then brainstorm or ponder, mill and win.
Combo 4
Chaingun/ Infinite Mana
Do not fear no lab maniac is needed in this combo. First play Mikaeus then Triskelion and a phyrexian altar (goblin bombardment works too, but you will not get infinite mana). Remove all the 1/1 counters from triskelion dealing 3 damage to an opponent or creature. Because it has a base p/ t it does not sac on its own. So, sac it with phyrexian altar getting one of any kind of mana. But, because it has undying it comes back with another 1/1 counter you can remove. You may either chaingun your opponent until they are dead or win the game by using creatures like blightsteel colossus to wreck your opponent.
Combo 5
Chaingun
This one is a lot like the triskelion combo, but is different enough it gets its own spot. So, like last time play mikaeus, but next a pentavus, a disciple of the vault and a phyrexian altar (only phyrexian altar will work). Now tap one colorless to remove a 1/1 counter from pentavus and put a 1/1 colorless pentavite with flying onto the battlefield. Sac the pentavite with the altar for colorless. Then remove another counter, and repeat. After five times it will self sac, because it has no base p/t. When it is put into the graveyard disciple of the vault will deal one damage to an opponent. Because it has undying it will come back for you to do all over again.
Combo 6
Infinite Creature removal (sort of)
This last one won't automatically win you the game, but thought i would include it in here any way. It is a fairly simple two card combo revolving around battlefield thaumaturge and curse of the swine. Now, i want to give you a fair warning about this combo, IT DOES NOT GET RID OF ANY CREATURES IT ONLY REPLACES THEM!!!! This means use this to exile those big ass cards but, not on 1/1 tokens. What it does is when the battlefield thaumaturge is on the battlefield if you cast curse of the swine the thaumaturge's ability will trigger allowing you target infinite creatures while still only paying the original cost of two mana. Then replace all the targeted creatures with 2/2 pigs. And BOOM you have just pissed someone off.
Number 3
Okay now that we are done with the combos lets tell you how to use the deck in game play. So its pretty easy, step 1, ramp mana like crazy. You can use cards like mana crypt and caged sun or sol ring as ramp artifacts. Step 2, make your opponents resources your own, with cards like stolen goods and grim return. Step 3, limit your opponents resources with bolas and herald of leshrac. While you are drawing cards with underworld connections and ponder. Step 4, get one of your combos out. If you cannot, argo your opponent with cards like thraxy and blood tyrant. Give yourself extra combat phases with cards like fury of the horde, and world at war.
And that is how you win a game of EDH.