Time: 09:46 GMT+1
Map: Summoners Rift
Champions: Sivir, Zoe
Sivir Spellshield (E) can block a variety of things, including the stun effect of the 4th AA against a target marked by Braums Passive. However, it wont block the Sleep effect from Zoe's E that kicks in after a short delay after being hit.
Several times in my recent match I was hit by Zoe's E, saw the timer on myself, activated Spellshield and was put to sleep regardless, whereas it can stop other timed/triggered effects such as Brand Passive or Braum Passive.