Considerations

DarkStarStorm,

Love your deck (+1)!!! I swapped a few cards I was running with some of yours, I am going to try out Vindictive Lich and Filigree Familiar, but Death Cloud is a stroke of genius!!! I was running Jokulhaups and that was mostly successful.

I have a couple of recommendations for you as well, I think you should swap your Sifter of Skulls for Pawn of Ulamog. Pawn is cheaper, makes makes a spawn if it dies, and it's a vampire which matters sometimes (Patron of the Vein and Metallic Mimic.

Also, I would swap Wurmcoil Engine with Kokusho, the Evening Star. It has flying and when it dies it usually nets you 15 life and dishes out 15 damage (5 for each opponent). With a graft creature (see below) you are able to dish out 20 damage/round and heal 80 life.

My meta must be different than yours as well because I have a really hard time with enchantments and you seem to be running light on enchantment "answers" like All Is Dust.

My last and most important recommendation is creatures with the keyword "graft" e.g. Vigean Graftmage (which I see you are running but I run them all). Here is why, if you control a graft creature and another creature comes into play under your control (by casting it or by Marchesa's ability) you can put a +1 counter on the creature as soon as it hits the battlefield, no dethrone required. If you control your commander and a sac outlet as well, you can sac the creature and trigger it's enter the battlefield or death trigger on each of your opponents turns as well as your own (~4x/turn). just dont forget to sac your graft creature while it still has one +1 counter and when they all return to the battlefield stack the triggers so the Graft creature enters the battlefield first so it can redistribute the +1 counters.

Please come check out my Marchesa deck as well. Marchesa, Death & Betrayal

MagicBlake Great input here! I was mainly running the Sifter of Skulls because it's more aggressive than Pawn. The plus one power doesn't seem like much, but it's the difference between one dethrone trigger presenting lethal and two. I may just run both! It's certainly a powerful effect. Kokusho I don't like because it is guaranteed to put you outside of dethrone range for the foreseeable future. You get use out of Wurmcoil even if you don't want to gain life. I have the option of blocking/attacking with the lifelink token. Otherwise Kokusho is simply a big flying beater. I will certainly consider Jokulhaups. Thankfully Death Cloud has not attracted any hate from my playgroup considering that the game ends shortly after I cast it. Jokulhaups should be in a similar state.

All Is Dust is really a poor option. You lose sac outlets in the process of clearing out a Sphere of Safety that you can simply win over the top of with Blood Artist effects. You don't need to attack to win in a Marchesa list. IF I need to get someone's Island Sanctuary off the field, then Nicol Bolas, Planeswalker, Nevermaker, and Dominus of Fealty are sufficient. Cyclonic Rift is a fantastic choice as well, but I am voting for its ban with its exclusion from my list.

I agree that Graft creatures are good in the deck, but most of them have mediocre to extremely weak effects outside of their use in protecting your board and being a sac target each turn. Both of those result in a useless deck if sac outlets or your commander are kept off of the field. That's why I run substitutes like Metallic Mimic, Olivia, Mobilized for War, Unspeakable Symbol, Mikaeus, the Unhallowed, as well as creatures that enter with counters natively. If the graft creatures had any effects that were even decently powerful on their own, I'd consider running them along Cytoplast Manipulator. As it stands, its substitutes outclass it.