Guide: Spectral Fist specialist

Here's how I got Spectral Fist specialist with 10:23 remaining.

In the screenshot I have Arcane Splinters. That was a complete misclick. You should only take Spectral Fist, and upgrade it with Ground Pound as soon as possible. I don't know if Spectral Clutch is good or if it sabotages getting the achievement; I was so well on my way to get the achievement that I didn't want to risk taking it.

Map: Haunted Caverns (the first map) in agony mode

Class: Sage, multiclassed into archer

Items: mark of the arrow; mask of madness; holy relic; iron ring; collar of confidence; firewalker boots; blood-soaked shirt; bloodstained wrapping (attack speed and multi-attack and spellcaster gloves don't work; bloodstained wrapping helps mitigate mask of madness damage)

weapon proficiency: take pinpoint 1 - 4, and also take strengthen at 1, 2 and 4 (you don't have enough memory pots for strengthen 3)

proficient stance: concentration 1 - 4

dedication: survival 1-3 to survive, and focus mind 4 because it's doubly effective

spectral fists:

1: power

2: precision

3: adaption (x2 via Reverberant Tincture), conversion

4: precision

5: power

6: adaption (x2 via Reverberant Tincture), precision, conversion

7: power

8: precision

9: size

10: adaption (x2 via Reverberant Tincture), conversion, precision

Traits: banish attack speed and multiattack (they don't work with spectral fist). Banish vitality and parry and thick hide and long fingers (they're low-impact).

Force, area and range all work and are all useful. Demonic Exchange (damage) is risky but worth taking.

The only tricky part is that you need to be somewhat good at dodging and moving efficiently in order to stay alive.