Here's how the CW describes him:
In this new iteration, The Trickster is an anarchist terrorist con man serving a life sentence in Iron Heights who helps Barry (Grant Gustin) and Det. West (Jesse L. Martin) to foil the city-wide attacks of a wannabe Trickster eagerly following in the original's deadly footsteps. The episode will reunite him with John Wesley Shipp who went up against him as the original 'Flash' on the CBS version.Funny enough, no one else has played The Trickster (other than a quick stint in DC Universe Online) other than Hamill, even in animated form, where he took on the role again in Justice League United.
I'm not exactly in love with the show, it's still got its fair share of CW-isms, but it's a good deal more fun than any other superhero show on the air. This is one more exciting development in a line of them.