For reference, oldies here:
Phasing basically reads: At the end of your untap step, if this is phased out, it phases in and vice versa.
Phasing out/in is like exiling, except it keeps all it's auras, counters, and doesn't "come back into play" in the literal sense. It's as close as the creature could be to actually being in play, but not dying to
wrath of god.
This gave them room to play around with downsides like
tefari's isle, or a new way to do the growing creature like with
warping wurm. Both those cards are awful, granted, but it's a downside mechanic they didn't push because creatures sucked ass back then. What do you want?
I'd argue if it were present on a few more cards, it could be interesting.
Crystal Golem was essentially
Obzedat, Ghost council at uncommon about 20 years earlier.
Katabatic winds (In addition to having a kickass name) is a really cool hosing card, and phasing allowed you to do really mean things but still have it be fair.
"Phases Out" was also the origional
AEtherling wording back in the day, with cards like
mist dragon and
rainbow effreet.
Also:
Reality Ripple sees some niche legacy play because of how phasing works. When a creature phases out, it brings all equipment, auras, counters with it. However, when tokens phase out (just like when you try and flicker them) they cease to exist. So phasing out
batterskull's germ token leaves batterskull phased out, wondering when it's time to come back in and beat down.
Flanking I've been over before, and while it's far too complicated for no particular reason, the net effect it has on gameplay is you get to do the same basic process as group blocking (creatures team up, you divide damage among them) while attacking. Keywords also get shared among the band, so cards with flying and banding almost let you jump creatures past blockers (assuming they don't have any air defense)
Also, to give it some value while blocking, banding lets you distribute damage among your band
however you want. Brawling with emrakul?
belenish hero can take all 15 for you! Giant pitched battle against an opposing fatty? Throw damage around until each creature is one hit from death, but kill the creature anyway!
It's actually really awesome, and has some sweet gameplay moments. But the mechanic really does depend on both players knowing how banding works, most of which is really hard to explain in reminder text, so the mechanic got scrapped.
But play some shandalar sometime. White Weenie kicks some ass in the early game with it, before everything gets all lotus-y