So you want to generate custom MTG cards
Yidris, Maelstrom Wielder gives cascade to all the spells you play each turn after hes dealt combat damage to your opponent, which at some point will inevitably end up in a storm of random spells to enter the battlefield all in one turn and cause a huge mess

Around 40% of my matches on Magic Online have been with the Naya version of this deck, but to show you how this deck has been doing, here are my results with the G/W version on Magic Online (a mix of 8 player queues and daily events, no two player queues): 2-0 v Abzan Control 2-0 v Mono-Red Aggro (He went big with Sakhan, the Dragonspeaker, Stormbreath Dragon, Shaman of the Great Hunt, and Flamewake Phoenix after board.) 1-2 v Mono-Red Aggro 1-2 v R/W Aggro 2-1 v Mardu 2-1 v R/W 2-1 v Waste Not 1-2 v W/U Heroic 2-0 v U/B Control 2-0 v Sultai Reanimator 2-0 v W/B control 2-0 v Jeskai Tokens 2-0 v G/R Devotion 2-0 v Mono-Red Aggro 0-2 v Abzan Aggro 2-0 v Abzan Control 0-2 v Abzan Control 2-0 v Abzan Reanimator 2-1 v R/G Aggro 2-0 v W/B Tokens 2-1 v Abzan Aggro 2-1 v Temur Devotion 2-0 v R/W Aggro 2-1 v G/R Devotion 2-1 v W/U Heroic 1-2 v Mono-Red Aggro 0-2 v Abzan Control 1-2 v Mono-Red Aggro 1-2 v Mono-Red Heroic 2-0 v Sultai Control 2-0 v Sultai Reanimator 1-0 v Abzan Reanimator (He conceded the match after asking for my decklist) 2-0 v Temur 2-0 v Temur Planeswalker Control 0-2 v R/W Aggro 0-2 v R/W Aggro 1-2 v Sultai Control 2-0 v Green Devotion 2-1 v Abzan Control 2-0 v U/B Control 2-1 v U/B Control 2-0 v Sultai Control 0-1 v Abzan Control (timed out) *Losses are in bold Thats a total record of 30-13, certainly worse than when I was 20-5, but still respectable

If you do, that creature enters with that many additional +1/+1 counters on it