This type of effect is most powerful in mono-black, where you'll have a lot of Swamps to play with, but can also be very effective in simple dual-colored decks
There are some stipulations, however, but it's relatively easy to meet them
WotC found Breach, especially with Mox Opal, made for a combo deck that was too fast, resilient, and non-interactive, even winning on turn one
In a recent Good Morning Magic video, designer Chris Mooney says there was always a plan to create more My Little Pony cards, as you can see from Twilight Sparkle's ability, referencing pony cards that had not yet been released
I literally just started learning about Pokemon cards and ran into the topic without knowing it existed many times
As if this somehow werent enough, March of the Machines enables even more combo potential