The dealer wins on the dealt hand.
The dealer wins immediately on the opening fourteen tiles, before any discard is made. It is a limit hand.
Nothing is drawn, claimed or discarded first, which is what makes it heavenly. Only the dealer can score it, since only the dealer starts with fourteen tiles.
There is nothing to build. It is dealt or it is not. What it does reward is checking your opening hand carefully before your first discard, because a complete hand you fail to notice is a limit hand thrown away.
Discarding before looking. The hand is scored on the tiles as dealt, so the chance is gone the moment you play a tile. Our table checks for it automatically, but at a physical table the responsibility is yours.
Nothing adds to it. It is a limit hand by itself, and the win happens before any other condition could apply.
Can a non-dealer score it?
No. Only the dealer holds fourteen tiles at the deal. The non-dealer equivalent is Earthly Hand.
Does the hand still need to be a valid winning shape?
Yes. Fourteen tiles must form four sets and a pair, or one of the special hands.
How often does it happen?
Almost never. Most players go their whole lives without seeing one.
Play Mahjong Winds
Every win shows its faan line by line, using the table on this page.