The god of Zombies

So I only have a little advice from playing Sidisi Brood tyrant edh.

Minds desire is cool, but you just don't have enough way to take advantage of it, id swap it for one of the things I suggest below.

Phenax is fine, but just doesn't do enough on his own, your milling yourself enough. If you want to mill opponents just run windfall to make fewer enemies and have more mana left over to get things back.

As your gods ability doesn't trigger prized amalgam (you exile the creature then copy it I think?) id say he just isn't worth it. If you want repeatable sacrifice fodder, your better off running grave crawler.

Id swap out more of your self mill cards to add in the aggressively interactive cards in your sb, Such as fleshbag, custody litch and dark salvation. Only do this if your meta needs it though. Id keep them close by the deck, sort of as a sideboard to adjust to the decks your opponents pick.

Cards like thought vessel and burnished heart should only be added if you feel you need the ramp, if the deck functions five over 6 games and doesn't have mana issues in at least 4 of them you probably don't need those cards.

The other possible cards don't seem to have much value to me.

One last bit of advice,
Run nimble obstructionist (the NOPE! bird as I call it) and willbender to counter bjuka bog, and other exile effects as often times that can end your game.