It can give a creature islandwalk to sneak past an opponent with islands, shrink something by -1 toughness while adding +2 power to push through damage, or even force a player to discard a card
Sneaking through your small creatures is a great way to gain Max Speed, mind you
It can be played in various rule formats, which fall into two categories: constructed and limited
Does a Flickered Creature Have Summoning Sickness
Being able to occasionally steal an Aether Vial for tempo, a Dragons Rage Channeler, a hammered Memnite or a Kaldra Compleat germ token is cool, and happens more often than one would think
They were right, but the thing is they have quite a ridiculous level of reach into the community compared to the likes of me