[quote=Ammokkx]
<Snipped quote by Scarifar>

Not quite. When it loses its overlays, it's still in the game. The overshift happens when you try to detach something that isn't there.

Edit: Well, more specifically, when you try to activate an effect without the overlays. [b]A phase shift monster can have its effect as long as it has overlays, but the moment those are used up the effect is negated and they retain the attack and defense of the last phase. [/b]Once you can activate one of their effects, gain the appropriate phase, and at the end of the turn you did that it is banished.
[/quote]

This explplanation here helped me make sense of Phase Shift monsters, though the part where effects are negated after the overlays are gone makes me think: if you are meant to detach the second willingly, then what is the point of doing so if the effects just get negated? The whole Overshifting part didn't make sense after that, so I opt to ignore the effect negation and merely stick with Phase Shift monsters just getting banished at the end phase. Does that sound good to you guys?