Credit to Zorthas on Twitter
Not to be confused with the character-specific discount removing crest costs for upgrading another piece of gear to the same item level on that particularly character, these seasonal achievements mark the point at which that character's gear has grown beyond each upgrade track, unlocking the ability to trade crests upward into their higher versions and a big discount for that particular type of crest on alts. Previously in Dragonflight and The War Within, this discount was only 33%, but has been raised to 50% in Midnight.
Adventurer of the Dawn discounts Adventurer track upgrades for alts, and allows uptrading Adventurer crests into Veteran.
Veteran of the Dawn discounts Veteran track upgrades for alts, and allows uptrading Veteran crests into Champion.
Champion of the Dawn discounts Champion track upgrades for alts, and allows uptrading Champion crests into Hero.
Hero of the Dawn discounts Hero track upgrades for alts, and allows uptrading Hero crests into Myth.
Myth of the Dawn discounts Myth track upgrades for alts.
The discount applies separately for each achievement, so in this case the Champion track is discounted, while Hero is not.
The upgrade system has undergone several other big changes in Midnight, streamlining the use of currencies to try to mitigate the amount of resource hoarding and using drops to save on upgrades.
Upgrades now require a small amount of gold instead of Valorstones
All tracks have an equal six ranks and only use their associated crest, instead of overlapping.
The number of crests required to upgrade increases with each subsequent upgrade along the track.
While this requires a lot more crests to finish upgrading overall, this is also probably why the discount was changed, as 33% split evenly from 15 discounted to 10, but is more awkward for upgrades costing 40 being reduced down to 26 or 27. In any event, it should reduce the amount of time farming crests on alts, making them much faster to gear out and catch up to your main.
