The Hardest Objectives Needed to Earn Diablo 4 Season 5's Secret Title

wowhead.com:

Diablo 4's Diablo 4 Season 5 hasn't even been out for a week, and it looks like its hidden Season Journey title has already been found. While most players are still working through their Seasonal Objectives, one Redditor has just completed their journey and discovered the hidden achievement, Istel's Begrudging Ally.

According to Wastelad's recent post, this secret achievement is earned by completing every Season Objective in the Season of The Infernal Hordes, much like previous secret titles. Even with an expected acquisition method, though, this is still a great feat for so early in the Season — congratulations on your new title, Wastelad!

Source: Reddit

Players have been able to earn hidden achievements like this one in every Diablo 4 Season thus far, but the difficulty in attaining these achievements can vary wildly depending on the objectives.

There are typically an abundance of easily-obtained «freebie» objectives, such as «Craft Elixirs at the Alchemist» and «Equip Sacred Legendary items in every slot,» but there are usually some relatively difficult-to-obtain objectives as well.

This season, three Season Journey objectives stood out to us as the most difficult, whether it was because the content was inherently challenging or simply more time-consuming than others:

1. The Gathering Fires — Acquire 6,666 Cinders during Helltide in Torment IV
   This one is not necessarily difficult in the traditional sense, it's the obligation that it implies — and the time. Collecting Cinders during the Helltide is easy, but this achievement requires you to collect them in World Tier 4 specifically, and by the time you're in World Tier 4, you're more likely to have moved on to bigger and better endgame activities. Players are generally diving into The Pit, focusing on the new Infernal Hordes mechanic, and starting their endgame grinds, so spending time in Helltides might be seen as «wasted» at this point in the leveling process.
   
2. Damnation's Downfall — Defeat 20 Helltide