If Faceless Void used Chronosphere, would Riki be able to blink to him using Blink Strike and then backstab him (with Blink Strike)?
There are a few unknowns here.
For this to work Riki would have to be outside of the Chronosphere when casting blink strike. If Riki also would like to attack, Void would have to be standing on the edge of the Chronosphere so that Riki isn't caught in the Chronosphere upon blinking to the back of Void.
Damage will be dealt to Void as the cast of Blink Strike goes through (40/70/100), however auto attack damage will only happen if Riki is actually able to attack.