This hero is very powerful and if you know the right strategy to play, most likely you will always be able to get 1 step ahead of your enemies, or when needed you will be able to disappear fast. As you know this is an Intelligence HERO but, i mean a huge BUT, this hero's strength resides in his STRENGTH and hp.
Of course you will need to buy intelligence items or combinations but you always should get some strength items or combine with intelligence for best effects. This hero is strong and has huge health. OK, now that we know about the items you should buy let's see the, abracadabra, the spells: I don't know if this is the most important spell in it's pocket but for me this is the primary spellHeartstopper Aura (T)"The Dirge's deathly air stills the hearts of his opponents, causing them to lose 1% of their max health over time."
In an 1000 AOE at lvl 4. And most importantly this spell is passive so it is always active, no mana needed. I just love it when they are in range and start loosing there health, sometimes when they flee a fight they will die while running. HAHAHA Another important spell is Raise Dead (D)"Calls the Undying' s fellow zombies out of the earth to fight. Once a zombie attacks six times, another one will rise alongside it. When a zombie dies, its reanimating life force returns to Dirge, healing him by 50 hp. Lasts 30 seconds."
These zombies are just awesome, you can summon as many as 4 Zombies at lvl 4 for 160 mana cost, but as they fight they will be more and if you buy some aura giving items they will last for sure and you will have a huge army which will heal you when it dies so it's a good deal for sure. This has a 30 second cooldown to cast. Soul Rip (R)"Redirects the flow of living energy through a target friend or foe, damaging them or healing them depending on how many unites are near it." So at lvl 4 it damages or heals for 20 points x as many units the target has beside it. if there is a huge army then you can make the math...
This spell is very useful has 30 seconds cooldown and you can cast it for 125 mana at lvl 4, i don't use it that much coz it don't do much on 1on1 only if there allot of creeps/units. Your ultimate is Awesome i like this ultimate it is like poison every one gets infected.Plague (E)"Infects the target with a plague. Reduces movement speed by 30% and amplifies incoming damage. Infects other units that come within range of a plagued unit." Wow at lvl 3 it amplifies damage by 35% that is enough for any hero to die in that encounter well of course unless he's scared and manages to run away. This has only 45 seconds cooldown, and a mana cost of 150.