Upon casting a time stop spell, the magic-user causes the flow of time to stop in the area of effect, and outside this area the sphere simply seems to shimmer for an instant. During the period of spell duration, the magic-user can move and act freely within the area where time is stopped, but all other creatures there are frozen in their actions, for they are literally between ticks of the time clock, and the spell duration is subjective to the caster. No creature can enter the area of effect without being stopped in time also, and if the magic-user leaves it, he or she immediately negates the spell. When spell duration ceases, the magic-user will again be operating in normal time.