StoriedStoried is a static ability. It means “Any time you control three or more permanents that are artifacts, Sagas, and/or legendary and you don’t have an enduring story, you have an enduring story for the rest of the game.”
Enduring story is a designation that has no rules meaning other than to act as a marker that other rules and effects can identify. Any number of players may have the enduring story designation at the same time.
After a player gets an enduring story, continuous effects are reapplied before the game checks to see if the game state or preceding events have matched any trigger conditions. (CR 702.195) (If you control three or more artifacts, legendaries, and/or Sagas, you have an enduring story for the rest of the game.)
Whenever Balin or another Dwarf you control enters, you may
discardTo discard a card, move it from its owner’s hand to that player’s graveyard.
By default, effects that cause a player to discard a card allow the affected player to choose which card to discard. Some effects, however, require a random discard or allow another player to choose which card is discarded.
If a card is discarded, but an effect causes it to be put into a hidden zone instead of into its owner’s graveyard without being revealed, all values of that card’s characteristics are considered to be undefined. If a card is discarded this way to pay a cost that specifies a characteristic about the discarded card, that cost payment is illegal; the game returns to the moment before the cost was paid (see rule 733, “Handling Illegal Actions”). (CR 701.9) your hand. Draw X cards, where X is the number of cards discarded this way. If you have an enduring story, Balin deals X damage to each opponent.