This is the build I use for [Xaku].

Ability range is THE most important stat to max out. Range is what determines how many guns the 2 (Grasp of [Lohk]) will grab, with a max of 16.

Ability strength is mildly important. Since [Xaku]'s 2 scales with enemy level, having incredibly high ability strength is unimportant. However, having enough ability strength to make the armor reduction for their 3 (The Lost: [Gaze]) is vital, especially for the steel path. With this build, the armor reduction is 89%, the highest I could eke out with just mods whilst also maintaining the required ability range.

Ability duration is also mildly important, probably more-so than strength. How long the first three abilities last for doesn't matter too much, seeing as their 4 (The Vast Untime) freezes the timers for those. However, if you don't want to constantly be managing energy because you've turned into an energy vampire, some extra duration is required. I did what I could with mods, but you can eke out more with archon shards.

Now, the archon shards I used were to my personal preference. I wasn't happy with [Xaku]'s armor or max energy, so I used two tauforged azure shards to provide each. I also used a tauforged amber shard to aid with energy pickups which, when in tandem with Arcane Energize, works almost perfectly for energy management. As for the last two shard slots, those went to tauforged crimson shards. However, these shards were NOT used for ability strength but rather for duration--remember, the damage of the 2 scales with enemy level, and there's already more than enough armor reduction for the 3.

The updated stats with the archon shards added in are:
Armor - 403
Energy - 305
Duration - 158%

Thank you for reading, and thank you for coming to my TED talk.