I missed something

[UManiac]

in the Avengers when Electro sprung the inmates of the Raft he took one prisoner:

who was the prisoner?

why was the prisoner important?

has this story line been developed further in any book? if so where?

who was the mastermind behind the plot?

[tigerkaya]

in the Avengers when Electro sprung the inmates of the Raft he took one prisoner:

who was the prisoner?

why was the prisoner important?

has this story line been developed further in any book? if so where?

who was the mastermind behind the plot?

The prisoner was Sauron.

[ImmortalIronFist]

in the Avengers when Electro sprung the inmates of the Raft he took one prisoner:

who was the prisoner?

why was the prisoner important?

has this story line been developed further in any book? if so where?

who was the mastermind behind the plot?

Electro broke out Sauron (Karl Lykos). He was hired by the Hand while it was controlled by Elektra. At the time, she was being impersonated by a Skrull. Sauron was just a reason for all the criminals to be released to create more chaos as part of the Skrull's plan to take over the world. I don't know why it was Sauron specifically though.

[deathcry]

I was going to say that in retrospect, it was kind of stupid to be Sauron. He fled to the Savage Land, and the New Avengers followed, and there they discovered the 'bogus' SHIELD (actually Skrull) agents there.
Of course, the Skrulls didn't know the Avengers would get back together (though should have thought of that possibility).
But as I was typing this, it could have been part of their plot for the heroes to discover SHIELD agents to sow further distrust (and/or possibly nuke the Avengers out of existence).
Was it ever noted whether Black Widow II was a skrull or not?

[Brother Justin Crowe]

Was it ever noted whether Black Widow II was a skrull or not?

She was visited by one after she got the Adaptoid beaten out of her, that much we know. The real Yelena showed up at the end of the T-Bolts arc "Widowmaker" (literally, on the last page), but nothing was done with her after that.

[strathcona]

She was visited by one after she got the Adaptoid beaten out of her, that much we know. The real Yelena showed up at the end of the T-Bolts arc "Widowmaker" (literally, on the last page), but nothing was done with her after that.

The real Yelena showed up as a member of a team with Blade, Micromax and Dominic Fortune in the short lived Marvel Comics Presents series before she was in T-Bolts... Though there was no connection to her being an Adaptoid mentioned there either.