At what speed does phasing happen?
Phasing is no faster or slower than any other fast effect, and fast effects resolve like instants. Let’s say I phase out my Wild Elephant with Reality Ripple and in response you cast Dark Banishing on my Wild Elephant. According to the last-in, first-out rule, the Dark Banishing resolves first, burying my Wild Elephant. Because it has no target, my phasing spell then fizzles. On the other hand, let’s say that you hit my Wild Elephant with Dark Banishing and in response, I phase the Elephant out. According to LIFO, my phasing spell resolves first and my Wild Elephant phases out. The Dark Banishing then resolves, but it has no target and therefore fizzles.