Do Zero Drive and Karthus Deathknell banish the same unit twice?
A unit with Zero Drive attached dies while Karthus is in play. Two Deathknell triggers are created — does the unit get banished twice?

Your [Deathknell] effects trigger an additional time.
Artist: League Splash Team
Card Set: Origins
A unit with Zero Drive attached dies while Karthus is in play. Two Deathknell triggers are created — does the unit get banished twice?
If Soraka, Wanderer and another unit at the same battlefield die at the same time, can Soraka's effect save the other unit as well? For comparison, in a similar simultaneous-death scenario with Karthus, Eternal and a Deathknell unit, the Deathknell still triggers twice — so is Soraka's case any different?
If Karthus creates another instance of a Deathknell, they resolve separately. Can I manage the order so I play one unit from the first Deathknell and then Vanguard Captain from the second to get Legion?
In a 2v2 match, does Karthus's ability apply to my teammate's Deathknells as well as my own?
I kill Karthus and Glasc Mixologist together with combat damage. Does Karthus see Mixologist die and spawn Deathknell twice? Can the same Karthus be revived by his own ability?