Well this certainly seems like a fun build around More on reddit.com

There is various way to build [[Indominus Rex, Alpha]] one way is to go more Voltron where you want more Haste in the Keywords and some +1/+1 stuff and the Voltron cards, its probably the fastest way to kill at least one player. The reanimation way is not exactly classic reanimation because you have Keywords creatures instead of game finisher and Indominus only fill the graveyard once. The other way i have chosen to build it is going more for a board control strategy abusing more the Indestrutible and Hexproof Keywords. I can put in more stuff like [[Pernicious Deed]] and [[Oblivion Stone]] getting Artifact and Enchantment to since we dont have many, i go lower in the +1/+1 stuff to do it and the board wipes also surve to clear the way for bigger attacks. The reanimation is more opportunistic and repeatable trying to get back the stuff i have discarted for a wider board. The chosen creatures are more of quality like Gods then just Keywords for Keywords. Here is my decklist with and old primer that i have made some change to since then: https://www.moxfield.com/decks/-vi7djdxvESVxyhObBLGuQ More on reddit.com

No major advice, but a small piece of tech. [[Breaker of creation]]. The way keywords work is that "hexproof from each color" is actually a shorthand for "hexproof from white, hexproof from blue...." This means that if you discard breaker of reality to your Rex trigger, you will draw 5 cards and it will have hexproof from all colors. More on reddit.com

I had success in building my [[Indominus Rex, Alpha]] deck but i did not go the Voltron way. The problem with going all in on Voltron is that you will probably be able to kill your first opponent but then you will struggle to deal with the rest of the table because you were scary from the start and the Voltron cards in your deck take the space of the cards that would allow you to deal with 3 oppenents. Indominus can still do the 3 shot commander damage kill by just giving it +1/+1 or a bit more later with cards you would put in the deck anyway like ; [[Biophagus]], [[Runadi, Behemoth Caller]], [[Rhonas the Indomitable]], [[Nylea, God of the Hunt]] or [[Avabruck Carataker]]. Something i see in a lot of decklist doing is using bad small Keywords creature just for Keywords, in term of Haste for an all in Voltron style that dont really care about reanimation that would be ok but if your going for reanimation sub-theme a [[Gurmag Swiftwing]] or [[Wilson, Rifined Grizzly]] is just bad targets. For the Reanimation part, since your doing Keyword its not gonna be your typical reanimation deck where you want to reanimate fast a big finisher and use a lot of space in your deck to put cards in your graveyard. Its better to look at it as an opportunistic reanimation where you put reanimation cards that fit the theme or dont take extra deck slot like lands, ramp or keywords card like [[Port of Karfell]], [[Tomb Fortress]], [[Honest Rutstein]], [[Nullpriest of Oblivion]] or [[Junji, the Midnight Sky]]. Secondly complet it with cards that can reanimate more than once for more resiliance. By using better quality Keyword creatures like Indestructible Gods and friends it will give you a deck that is more going Medium Wide with Resiliance. In my deck i have completed that with board control since Indestructible can keep you ahead of a wipe. I see in your list you already hace some free counterspell, removal specialy in mass is our enemy. Here is my decklist up to date as of now, [[Outcaster Trailblazer]] from the latest set helped me cast my commander and draw me lots of cards to win the last game i played. https://www.moxfield.com/decks/-vi7djdxvESVxyhObBLGuQ This style is jam pack with overlaping use for the cards, i have already use [[Mana Drain]] for ramp. By going this style drawing is importent and i recomand the clones of legends like [[Spark Double]] and friends not only will it help fill your yard but it will help that Medium Wide Resiliance strategy. The primer is not up to date from all the latest change but give a good call of what i'm going for. There is also a [[Miirym, Sentinel Wyrm]] decklist with primer and a Sphinx tribal list in [[Yennett, Cryptic Sovereign]], i see 2 decks in your list that can use inspiration from those. More on reddit.com