Slow Cube

[HugPhoenix]

Lets slow down the meta shall we?

[spoiler=original]

[spoiler='lore']Both players can only summon/set once per turn.
Once per turn: Negate any effect that targets this card.[/spoiler]

[/spoiler]

[spoiler=lore]Must be the first card activated during main phase 1. The effects of face-up monsters with 2300 ATK or more are negated. Both players can only summon/set once per turn.
Once per turn: Negate any effect that targets this card. You must pay 500 life points during each of your end phases. If you cannot, this card is destroyed.[/spoiler]

[AGATHODAIMON BANGTAIL COW]

Oooooor you can Summon like crazy on your turn, play this during the MP2, and laugh as your opponent completely and utterly fails to use their Extra Deck at all because you won't let them get enough monsters on the board. Plus they can't flat-out MST it since this negs the first thing to target it. Pretty much the only relevant cards that could get around this are JD and Artifact Moralltach (it doesn't target for that effect). To avoid this sort of situation, you can make it so that it has to be the first play you make in a turn.

 

Even then, this card simply destroys the game as it slows down everything to the speed that gelatinous cubes in D&D have. You pretty much take three turns to Summon a miniboss like Caingorgorm or Diamond Crab King (though Hyperion, JD and Grapha don't care about this slowness as much as they can just slap themselves onto the field). You're not slowing down just the meta, you're slowing down anything that could possibly Summon more than one monster per turn, and this incredible change in pace is going to make duels become lengthy and boring.

[HugPhoenix]

Total overhaul

[AGATHODAIMON BANGTAIL COW]

Well, it now stops you from playing explosively and then slowing the game to a halt, but the thing is that this can still slow the game down to a complete standstill. The part of slowing the game down to the speed Yugioh had a decade ago is the problem here. Really. The random no-effects-for-monsters-with-2300+ATK prevents Lightsworns from taking it out with JD, and also randomly makes Indomitable Fighter Lei Lei much more powerful (Goblin Attack Force as well to an extent, but Lei Lei is much more searchable). That doesn't solve the problem at all, all it does it turn sacky bosses into vanillas (who are still good now that the game is way too slow). The maintenance cost is laughably ignorable and shouldn't really matter much.