He most certainly was among the 12, and sent out to do evangelical and healing work. There is no sign that he stood out or was antagonistic in any way.

Then, as we memorialize today, he took the biggest heel turn in the history of mankind. Its largely inexplicable. Some gospel authors indicate "the devil entered him". One seems to suggest he was motivated in his betrayal by money, asking the priests first "how much will you give me". Other accounts make the money seem almost like an afterthought. At least one has him giving it back after the deed.

Christians throughout the centuries have speculated that he was a political zealot, initially hopeful that the Christ would lead a nationalist rebellion against the Romans, and became disillusioned. There is no credible evidence in support of or against this theory.

He was paid about four months laborer's wage for the betrayal.

The narratival claim is that the priests did not want to make the arrest in the chaos of the Passover pilgrim crowds, and for this reason needed Judas. There's further speculation that Judas was needed to identify Jesus to the arresting soldiers. Ive seen people write, "it was dark, no nighttime illumination" etc.

This all seems curious to me. Jesus of Nazareth, even before an age of media, was likely very recognizable. Was he actively hiding? Were the 12 and the followers aggressive about opsec? There's no suggestion of this, apart from Peter initially drawing / using his sword at the arrest.

Why was Judas even necessary to the scheme to arrest Jesus?

And if necessary, couldnt he have pointed him out from the shadows? Why the kiss?

Perhaps it was all demoralization, for Jesus and the others. To demonstrate that the priests have reached even into the inner circle?

Its all curious.

There is also in Christianity a kind of perverse and beautiful tendency to build around sin (e.g. "O Felix Culpa!"), with the idea that each sin - even Adam's great crime - was necessary and in its way blessed, to set the wheels in motion for the Redemption.

You might imagine there could have developed some such understanding around Judas. His betrayal progressed the Event that saved us all from eternal damnation. He played his role, etc.

But no... there has never been anything but contempt for him, and there is no tradition that suggests anything but that he is eternally damned.

(http://www.autoadmit.com/thread.php?thread_id=5852328&forum_id=2#49785691)