Grindclock and Tezzeret the Seeker are really ugly together.

Eater of the Dead usually goes infinite with Phenax on the field if you're looking for that kind of thing! He seems to be a staple in Phenax EDH too. Umbral Mantle can be used multiple times to buff before the tap-to-mill ability resolves if you have the mana for it! For example, if you used the mill ability and untapped Phenax with the Mantle two times to buff him by +4 your opponent must mill 11 cards twice for a total of 22 cards!

Like that Eater of the Dead ! Will fit nicely into the deck. Oh and I am happy to say I pulled off my Mindcrank + Duskmantle Guildmage combo on an Infect deck!

Haha, that's very satisfying!

Have you considered Creeping Tar Pit for man land?

Also Drowned Catacomb .

I have thought about Creeping Tar Pit but it really doesn't fit in other than using it for land only. Drowned Catacomb I could use to replace a basic land.

Remember bloodchief ascension, that works well with Mincrank, if you like combo wins.

Oh that is nice! Only cost 1 swamp to play. Will have to find a spot for Bloodchief Ascension into this deck!

This is a good start for a Phenax deck! As you consider building it you need to remember that EDH is a format that favors card abuse and combos. You should stay away from cards that don't combo or have very limited effects like Curse of the Bloody Tome Paranoid Delusions Mind Rot Returned Centaur Tome Scour ...

You cannot mill someone to death if they have an eldrazi like Kozilek, Butcher of Truth in their deck. You either need a way to remove it form the game like Sadistic Sacrament or you need another strong way to win (Infect, powerful creatures, I WIN cards Laboratory Maniac , Commander damage)

You should be looking for things that get stronger and more effective as the game goes on or that can combo out to force a win or that are so powerful that they demand a response.

Also you don't want to forget to add a few of the cards in your colors that are so good that they MUST be considered for any deck containing those colors. One example would be Treachery ... that card is AMAZINGLY good.

Lastly, unless your deck type makes a special use of basic lands you should be looking to have more powerful lands in your deck. IE: Volrath's Stronghold or Academy Ruins

If you look through my Phenax deck I'm sure you'll find a few things that you'd like to include in your own deck. Best of luck to you!

Serpent's Guile and Serpent's Fangs!

@ Zacoly my deck is built for milling my opponent with a lot of defense. With what I have built above I've played games where my opponent recycled their graveyard back into their Library and I still milled them out! Hence all the fat bottom walls which go well with Phenax, God of Deception . So far this deck has held its own, but like every deck it's the luck of the draw that makes or breaks it! Not everyone can drop money on a $50 card just to make their deck better. Now I do need to add a couple board wipes like Nevinyrral's Disk or Extinguish All Hope . Also remember that I have Meekstone to keep the more powerful creatures from untapping and the reason for that is a majority of my walls' power is zero.

Leyline of the Void words well to combat the eldrazi

it might be good to replace Doom Blade with a better kill spell if available: Silence the Believers or Hero's Downfall come to mind. also, something to deal with any annoying artifacts/enchantments would be good. the options are low in U/B, but some form of Boomerang effect that returns any type of permanent would be a good thing to include. pair it with a counter spell if it's a particularly difficult to deal with card. a bounce or more counters might do better for you than your one-time use mill spells, like Tome Scour as nice as they are, they don't cantrip and your creatures should be able to get the mill wins without them.

forgot to mention, Tidal Force is really nice in a phenax build if you can get one, 7 mill per turn no matter who's taking the turn is just awesome. probably better than a Guardian of the Ages

have you considered Rise of the Dark Realms or Sepulchral Primordial ?

think about Lazav, Dimir Mastermind he's awesome. the bad news about mill-focused commander is the big eldrazi. the good news is they hit the graveyard before they shuffle. someone gets to shuffle their graveyard because of an ulamog milled. well you get to have a ulamog on the field, now you can win by damage. oh he's hexproof now. before he makes a copy he's a fantastic devotion enabler.

Another good card you can add is King Macar, the Gold-Cursed . Excellent spot removal with Phenox on the board.

I give a +1 just cause I build a deck like this. mine had more control but same mill style

Umbral Mantle

Pemmin's Aura for shit and giggle. Put it on your commander and it becomes : pay U, mill 7