From Dimir Control to Rakdos Midrange, any black deck that runs creatures or looks to answer them leans on Fatal Push to stay alive in the early turns
You play them in the same way you play other cards that fit multiple roles, to smooth out your ratios and effects
The only trick is figuring out how to activate delirium, but with so many discard outlets in red, that shouldn't be too hard
This was mimicked stateside by being a part of 24 of the top 64 decks of the 2018-2019 Madison Regional Championships, with the exact same list placing 2nd, 3rd, 6th, 10th, 23rd and 30th.
No matter what type of deck youre building you should be running cards like Shaman of the Pack in your deck
While it requires a Lightning Energy to be powered up, this attack is much more efficient than Keldeo EX