Maybe a couple Ruthless Deathfang and then Qarsi Sadist in place of Sultai Emissary as another sac outlet for Black Cat. Helps you control their board and makes them discard.

I know that doesn't fit tribal zombies, but having to sac a creature and discard cause you sac'd a Black Cat? And possibly flying over their head with Siren of the Silent Song?

+1 cause you started wheels turning in my head and I'm gonna have to brew a deck now.

you can check mine out for ideas, its tribal zombies with devotion.Previously on The Walking Dead...

dark deal + waste not could be good, with all your discard you should be able to get some zombies from waste not, and the dark deal triggers chasm skulker and waste not simultaneously.

Fliers, hmm Master of the Feast Would be good on your sideboard for early flier defense then Despise to control there hand since they will be getting an extra card draw. Hope that helps.

I just like the idea of dashing Zurgo Bellstriker and having Hero's Blade equip for free every time.

Interesting deck. i worry though about having 4X legendary creatures. maybe add some discard draws like Tormenting Voice that way you can filter your hand better. you look like you could deal fairly well agaisnt creatures mainboard so i might suggest some Negate sideboard. possibly even some Stymied Hopes since it scrys. also Anax and Cymede is a legendary that might be able to find a home here. depending on what you think youll be facing you can pack cards like Glare of Heresy in your sideboard or Gainsay. Surge of Righteousness, Rending Volley and Encase in Ice are also ok but i don't think theyll be quite as useful as some other cards mentioned.

I wish you the best of luck in your tournament.

I like the idea, but like aholder7 says, it might be kind of difficult with all legendary creatures. If you were going to do this, you could play a Heroes' Podium. Sure it's a high cmc, but you can get legendary creatures easily.