The first is that Army of One suffix, a reference to Lightnings powerful combo attack of that name in the gamean aggression that is symbolically matched in the card by giving her several offensive keywords like Trample (which lets her deal excess damage from combat directly to a player) and First Strike (which lets her deal damage before anyone else resolves damage in combat)
An EDH power level is basically a rough estimate of how well a deck can do what it is trying to do, especially when the other players are actively trying to stop it
Considering some of the best creatures in the game have that type, this is an incredibly valuable ability
This slots into so many decks looking to turn card draw into a bigger advantage for yourself - or punishment for your opponents
What it does do, though, is cheat creatures into play
mana creatures can be victims of removal spells, and artifacts that ramp can be answered by many different spells, but land destruction is a rare option