Challenge Rifts will come with the 2.6.0 patch.

Blizzard announced them last year, and these are pretty much randomized Greater Rift dungeons’ reimagination. They could be interesting for you simply because you can try more character builds/types without being forced to start all over from level 1.

Quoting Blizzard’s blog post: „Challenge Rifts are a weekly static version of a previously completed Greater Rift. To create a Challenge Rift, we pull a Greater Rift run directly from a player’s account. Once we have that snapshot, we make that exact character, including their items, paragon levels, skills, and gear available for everyone to play. This also includes an exact copy of the Greater Rift they completed with that character. Enemies, pylons, and the dungeons you encounter will all be exactly as they appeared when the original player completed their run. If you beat the original runner’s time, you’ll be rewarded with a weekly satchel filled with bounty and crafting materials and some Blood Shards.”

Replayability and challenge, even for veterans.