While its stats aren't much to write home about, thanks to its Landfall ability, whenever a land enters the battlefield under its owner's control, its owner may gain control of the target creature for as long as Roil Elemental remains in play
That being said, all the best red token generators can be roughly grouped into: Those that create Treasures, Those that create a copy of a creature you control, usually exiling or sacrificing it at the end of combat or end of turn, Those that spawn 1/1 creature tokens, Those that create some really big dragons
Both logic and science decide a type's weaknesses and resistances
(4/15/2013) The top card of your library isn't in your hand, so you can't suspend it, cycle it, discard it, or activate any of its activated abilities
I've barely mentioned half of them, with further objective types, event objectives available for limited time - but again, very generous and doable challenge - letting you pick up some special cosmetics like playmats and card covers