"Several new extra-dimensional Spiders have arrived just in time to help stop the spread of a powerful new drug, which gives users Spider-Totem like powers. Even with the additional Spider power offered by these new allies, the Spider-Army will be in a fight for survival, as a familiar enemy is chased from the shadows, and a new Spider hungry Inheritor reveals himself." — Chapter Briefing
The only way to recruit Silk is to complete the list of Tasks.
One of the Tasks requires the defeat of an Epic Boss. This can be done by having the requirements needed to unlock the Epic Boss or by skipping the task by paying 30 Gold.
The requirements are:
"Prison breaks and high tech drugs make up the backdrop of our Spider-Man's homecoming. It's a good thing too as the Symbiotes are on the warpath, with a Spider rich environment, where Carnage reigns." — Mission Preview
"The Inheritors scheme is revealed, and Silk is the key. Green Goblin, keen on maintaining a shaky alliance will do everything in his psychotic mind to keep her from S.H.I.E.L.D. and the Spider Army." — Mission Preview