(Note: This post is obsolete, mainly because I incorporated the idea into a larger post that features a comprehensive summoner spell rework.)
After a 0.25-second fading time, champion becomes stealthed for 1 second. Attacking or casting abilities, summoner spells or item effects will end the effect prematurely. Does not break stealth.
Fade is an idea I had for a stealth-granting summoner spell, to be picked by junglers as an alternative tofor ganks, stealth champions for supplemental cover and pretty much every other champion as a possible initiation/escape/positioning spell.
Currently, one of the problems with vision is that it's extremely cheap to purchase, and very effective. A warded lane, for example, is nearly impossible to gank properly. Having a dedicated summoner spell that'd grant stealth, even a very small amount, would offer a counter to vision, though the SS itself can be countered by a, which when not used against stealth champions is just picked to one-up the other laning support in the vision war.
Though the stealth duration itself is very small, it has the potential to let any champion position better in teamfights, as with Vayne and Kha'Zix. It'd also offer a means of escape or initiation which, despite its significantly lower cooldown relative to Flash, would have a lot more counterplay associated to it. Though it can boost the power of champions with existing stealth abilities ( Shaco, Twitch, Akali), the 1-second added duration wouldn't force too much of an advantage. What are your thoughts?