While Dusk Mage is very powerful I don't find it very fun to actually play. First of all is the fact that its better skills don't come until post level 15 which is already annoying as you will likely be in early act 2 by then in a game only 3 acts long! But also because Dusk Mage really doesn't have much of an identity unlike the Rail Master or Forged. Its a spellcaster and just like in most other games you pick them because they hit hard and little else.

Dusk Mage melts content and thanks to the staying power offered by the Blood Drinker relic, you are mostly unstoppable so while other classes have to work to get those insane power levels, Dusk Mage doesn't, without having any real drawbacks either. Balanced, as all things should be.

• Level 2 I recommend picking up Dark Spears for a few reasons. The main one is that we already start with a light based skill and Dusk Mage enters Harmonic form when you fill both the light and dark meter that you see on your UI which is done by dealing damage of those respective types. Dark Spears inflicts a slow in its area, lasts 9 seconds and helps charge your dark meter up very quickly. Basically its a swiss army knife of a skill and works fantastically well even with minimal investment.
  
  
• Level 5 I recommend 1 point in Blood Seekers so now you are not as reliant on potions and it will be one of our bread and butter survival tools anyway, it is super good and makes levelling go so much smoother! We will put more points into it later.
  
  
• Level 10 is 1 point in Living Barrier and by now the pattern is probably clear in that we are just tagging skills now that we intend to fill up later but Living Barrier is a great "Potion on a cooldown" skill and should be used accordingly as its duration is too short for anything else.
  
  
• Level 15 is what we have been waiting for and what a long wait it has been! This opens up Holy Fury which by now you should have enough spare points to take all the way to 10 immediately and will make up for all that skill point hoarding you've had to do until now. Holy Fury seems simple enough and it is but the way it works is this, as long as you hold the button down you continually deal damage and this works in the same way enviromental effects happen meaning it can rip through things very fast! Try stepping into fire in this game and you will know exactly what I mean! However it will also calculate on hit effects once every second so unlike Forged, Dusk Mage is not as good at stacking negative effects but it can still make use of them.
  
  
• Level 20, after pulling your hair out to hit level 15 and get your kill beam you will be happy to hear that there is nothing at Lv20 that we are desperate for. Bloodletter and Rupture are always nice to have for increasing DPS and Spinning Blade at lv3 to make it a passive can be useful but in all honestly you shouldn't be getting hit in melee frequently enough for it to pay off so its up to you. Energizer is normally a good skill to pick up for 5 points to increase Relic generation but we really will be mostly just back-filling the skills we picked up along the way and little else as we really are just a killing machine already.

Holy Fury is a great skill and it does everything you need a damaging skill to do but you will want to lace in some Dark Spears because mana will be an issue! On that note, Holy Fury does not "hit" for some reason? so Damnation mana gained on hit doesn't effect it. Holy Fury will enable other on-hit effects so this could just be a bug.

The way skills work in T3 is that skill effects are Global not local, that is if a skill says +20 Dark damage than all of your Dark spells receive that damage bonus, not just that one skill.
When it comes to back filling your skill points this creates lots of ways to min-max your damage and honestly Dusk Mage has no problems in the damage department anyway.

Blood Drinker relic also goes a long way to alleviate our fragility when its up and Dusk Mage has very little problems generating relic energy. Even mana regeneration isn't that big of a problem as it constantly regenerates anyway and the maxmum mana pool is really small at like 12? Just run around in circles for a little bit and it will be back. That said when bossing you really need to unload when the window is open and Harmonic Form has the problem that when it activates it is just a timer you have little control over whether you get to use it or not and It has the habit of triggering towards the end of fights or during phases where a boss might be immortal.

Energy Spike and Light Spear are not only really damaging skills in their own right but when taken to level 6 they increase the duration of Harmonic form by +50% and they stack granting +100% duration which is something to seriously consider even if you have no interest in using those skills because Harmonic Form not only increases mana regeneration thus allowing Holy Fury more uptime when bossing but it also increases damage too and is the secret to Dusk Mage being a killing machine, which can then rather insanely be augmented even further by Celestial Set; Gauntlets which adds a +50% damage to all skills and a +25% mana cost to skills but do you really need it? Very little can stand up to Dusk Mage as is, it's almost silly how much damage it puts out.

To talk more about Blood Drinker Relic it really is the de-facto "I want survivability" relic because it contains two healing skills on separate cooldowns and just has the Coldheart relic beaten in every way which is kind of sad but Coldheart is just a beginners trap because its immortality shenanigans seem good on paper but in reality when you enter phase dungeons or end-game, dying once means the end of your run. Fine, just don't die right? Well healing potions are not only on a premium because you can't leave a dungeon to go buy more but also because they have a cooldown and if you are stood in some fire you can't see (screen clutter becomes an issue!) with your potion on cooldown, your dead! Believe me, I have been there enough times and whats worse is building defence against burning now eats into your poison defence budget which is not only equally as deadly but unlike burning monsters, poison monsters serve as smart bombs with infinite duration so you can unknowingly have 5 poison bombs floating your way...

What I am trying to say is, the invincibility offered by Coldheart is not designed to deal with how damage in this game comes at you as it tends to only block a certain number of hits regardless of how much or how little damage those hits do so if an instant kill is coming your way and you pop your Ice Shield, some little goblin can strip it before you even noticed. This makes building lots of health a better investment so that you don't instantly die and all healing in this game is based on your maximum health which further encourages building even more health!