As the metagame currently stands, I would play two to three copies of the card, but I dont consider it to be a must-play like Prismatic Ending and Abundant Harvest
Each deck with have every card in 40k art, with a split of 58 reprints and 42 new cards in each of the 4 decks , making these attractive to MTG and 40k players who are interested alike
WotC is revealing one deck each day
This warlock wont help you storm off, but having a strong win condition in the command zone allows you to focus the 99 on being the best storm engine it can be
As always, any feedback is appreciated through my Twitter account @MelissaDeTora
Compare this to Two-Headed Hellkite , which is a 5/5 flying menace haste for one more mana that draws you two cards on attack