Out of curiosity, why arent you running Flayer of the Hatebound? On a different not, Triskelion goes infinite with Mikaeus, the Unhallowed. While you don't have to activate the combo, it's nice to have a panic button when you need it. Also, Dark Depths combos very well with Vampire Hexmage if you use depths, you should also run Thespian's Stage as a redundant piece. :)

Hi Scytec, Flayer of the Hatebound is a good one, i just don't really like the mechanic of machinegunning(is this even a word?) everyone on the table, but i'll probably add Triskelion. Dark Depths ins't that good at my table, a lot of bouncers and sacrifice shit. but i recognize that 2 20/20 flying indestructible is just broken.

Can't have 2 Marit Large tokens because they are legendary, Stage is just a way to cheat one out faster because it doesn't get the counters by entering the battlefield, it's already there so you can just tap, sac and go. :) Machinegunning is a totally viable descriptive term. :)

Oh, yeah, hate legendary tokens, but i can always sakashima the token :v But i don't know what to throw away to put the Triskelion or Dark Depths in, for the stage i would remove the Isolated Watchtower, it's a good ramp if i know my top card also it works like Scrying Sheets in a way, but isn't that effective cus i only run 6 basics. My mana base is good enough, i almost never miss my 4/5 drop, and beyond that i have like, 7 cards, since Dark Depths isn't a Mana Source, i can't remove a land to put it.

Diabolic Intent may be another valid card for you to consider. :p Sorry, I truly love Marchesa, she was my first non pre con commander. Duskmantle Guildmage, while excellent, feels lackluster here, you're turning things sideways, not playing an attrition game. Blade of the Bloodchief is another card I personally wouldn't run, though I understand your reasoning behind it. Dack's Duplicate is another thing I'd drop, but I've never been big on clone effects...too unreliable in my meta. Haha. You can see where my biases lie. I don't know your meta like you do, ultimately it's jyst a judgement call, but if you decide you made a mistake, you can always add back in whatever you removed.

I started to play magic around 6 months ago, edh has been my format for like 4 months now, i used to play Jeleva, Nephalia's Scourge before i learned that if she leaves the battlefield, i lose what i exiled. After this i started to use Marchesa, the Black Rose and i consider her to be my first Commander, i really love her, she's amazing. The Blade of the Bloodchief works lovely, so i will keep it. Dack's Duplicate is one of my best shapeshifters, and they sinergize well with Mikaeus, the Unhallowed cus i can copy him, sac for legendary ruling, return by undying copying another thing but they keep the counter. Duskmantle Seer* i use more to control my own life and carddraw, since it only happens on my upkeep i know i'm the first one to take out value of it, also it flies. I usually dislike tutors cus on my mind, if i'm going to play 100 different cards i don't want to just always go infinity, i'm build this to be powerful, cus the competitive aspect makes it more fun, but i don't want to archenemy my friends every single game. After i have this deck done, i'm going to build a competitive version of this, in a scale from The Command Zone,1 to 10, i want this to be a 6 to 8