See Lekwuhl, Sudden Oblivion.

Gosh. Zero-land decks, as long as you only need four colourless mana. That feels scarily potent.

How often would that come up outside of Legacy/Vintage, though?

Modern would probably like to only play 10 colored sources main deck

That's a good point.

Not even counting players that change their land base, this smooths over draws to such a degree that it makes mana screw a thing of the past. There's an argument in there for whether or not that's a good thing, but its undeniable that all tournament decks would auto run 2 or more of these in the sideboard.

Which brings up another point. If all of the cards in your sideboard are theoretically also cards in your main deck, does that remove strategy from the meta-game experience. And is that bad? There's a big conversation right now as to how Magic Arena's lean toward best of one matches is beginning to cut into meta-game strategies...

I recall jmg's issue being brought up when Cunning Wish and friends (most relevantly Living Wish, I guess) were legal. It's an option players have - dedicate sideboard slots to targets for things like Wishes or Mastermind's Acquisition, at the cost of sideboarding capability. A single card like this might not be too bad for tournaments.

But kitchen table is another thing entirely. Every single casual game would either have conversations like "Do you have your Slices with you? No? Can I borrow one of yours? Um, sure, I think I carry 4 in my wallet these days." Or have people feeling annoyed for not having the must-have cards.

I was thinking this might need to ETBT, but that wouldn't really help. Even making it cost 1 life to tap wouldn't help, actually: it'd just mean that your hail-Mary chance at not dying to manascrew often doesn't actually help you not die to manascrew.

If Magic had gone down this route from the get go, I'd quite like it. Imagine if these were just part of your standard gaming equipment that you carry around with you like dice or tokens. Great solution to manascrew worries. (Obviously coloured ones would be too good - make it far too easy to splash whatever and to get the colours for your splash just when you need it.) But I think it's too big of a change to try to make to the game now.

There are multiple mtg clones that have opted to have land cards in their own deck and rest of the cards in a second deck. So players could choose between drawing from either. One of those games being one called Force of Will.

For better or worse, mtg has decided it likes the "You randomly got manascrewed, hahaha" effect.

As a Hearthstone player, getting a guaranteed mana each turn makes the game worse. It becomes too predictable and the games play out the same too often, when the same card gets played on curve every single game

I made it Legendary, which solves some of the issues, though obviously not all of them.