Rad counters are put onto players, and trigger at the beginning of the first main phase of the active players turn (the one before combat)
The concept, the art, the story, everything about them makes the horror nerd in me really happy
Having a more simplistic way to bring in people, I see this as Wizards trying to revitalise Standard
Compared to some of the truly terrifying combos you can do in other games, Lorcanas biggest plays are more self-contained synergies that need a few turns to pick up steam
Hes arguably the best of the five in Limited play, where his ability is a blowout and you can seek to ramp him out a turn or two early, but hes close to worthless in any non-Limited format
The faster you chew up the mana dorks for extra cards and lands, the quicker you get to your giant threats