Season 23 starts on Friday, 2nd April.
A new Challenge Rift will become available on Monday, 29th March.
So, if you want to use the Challenge Rift reward cache’s contents to give your Season 23 heroes a head-start (i.e. train all your artisans, gamble bloodshards for legendaries, extract a legendary, upgrade a rare to legendary, and so on), do NOT complete it on Monday.
Wait until the season starts (scheduled for Friday at 17:00 CEST), create a seasonal hero, run the Challenge Rift, and collect the cache on the seasonal hero.
You can, of course, check out the Challenge Rift before Friday so that you can see what class / build / map layout you’re going to get, and to practice it, but do not kill the boss.
The bag contains:
475 bloodshards
5M gold (maybe little more or little less)
15 of each legendary crafting material
35 deaths breath
bunch of white/blue/yellow crafting mats
The amount of gold, bloodshards, death’s breaths and bounty materials are fixed.
The number of reusable parts, arcane dust and veiled crystals is slightly variable.