Illuminor Szeras provides such access thanks to his Secrets of the Soul ability which allows you to sacrifice another creature and add a number of black mana to your mana pool equal to the creature's mana value
Sphinx of the Steel Wind is a bullet you can Unmarked Grave to set up Dakkons ultimate in matchups where the opponent cant deal with it, which, realistically doesnt matter, but I thought it was cute to take advantage of, and it can also be part of the Gifts Ungiven package or your normal Persist plan
When you are going a blue mana denial route this card is one of your better options, if you are doing anything else this shouldn't be anywhere near your deck
You usually want to get the demon first in this case -- a 5-mana 6/6 Flyer is great, and then if you can start drawing cards and draining 2 life every time you do, the game's going to end in your favor
In general, this deck doesnt need to win the game as soon as possible - you can and will win long games, even against control decks
Being a creature makes it easier to answer, and it's more expensive, but the parallels are there
