Dual aurta gets its name from the vampiric aura(dread lord) and the unholy aura(death knight). Your main units will be ghouls.
Best verses: Dunno really dual aura isnt as popular as it used to be and I personally rarely use it.
Build order: 3 acolytes to mine, ghoul to lumber, cue 4th acolyte, build graveyard then crypt then back to mine, cue 5th acolyte, build zig, build alter, when crypt is done cue 2 ghouls, build zig, cue ghoul, then build tomb of relics. Hero you can either go Death Knight or Dread Lord first its your preference. Continue to pump out ghouls and up grade your necropolis to a halls of the dead so that you can get out your second hero. When u have a halls build a slaughter house and get 2 statues(1 mana and 1 life regen). If you went DK first i suggest creeping at least until level 3 so you can hav a lvl 2 death coil as it heals decent hp and does good damage at lvl 2. Upgrade halls of the dead to a Black Citadel so that you can get frenzy and lvl 3 upgrades for your ghouls. I wouldnt suggest getting a third hero simply so that your dk and dl get more xp and will lvl faster.
This build gets its name from the fact that fiends will be your main army. And there are 2 different ways of doing this build and that all depends on your hero preference.
Best versus: Orc. hit and run hit and run
Build order: 3 acolytes to mine, ghoul to lumber, cue 4th acolyte, build graveyard then crypt then back to mine, cue 5th acolyte, build zig, build alter, when crypt is done build 1 ghoul, build zig, cue fiend, build tomb of relics,(some prefer relics then fiend), the first hero will either be the death knight or the crypt lord both heros are a good choice the death knight can heal your fiends and the crypt lord makes bugs to tank for your fiends. if you like to power creep i suggest the crypt lord and if you do go crypt lord skill points should go bug, spiked armor, bug, impale, bug, ultimate, impale, impale, spike armor, spike armor. Continue to pump out fiends when at teir 2 get a slaughter house and upgrade burrow for your fiends. Get 2 statues again 1 mana 1hp regen. As far as web can either wait till enemy has air or u can upgrade it when its available your choice there. As far as 2nd heros if you went Death Knight first get the Lich King and if you went Crypt Lord either solo him or get the Death Knight. Ive never gone more then 2 heros with this build, never needed to :) Dont forget to focus fire!
This strategy is pretty self explanitory u make a shit load of gargs.
Best versus: Night elf. bye bye hunts
Build order: 3 acolytes to mine, ghoul to lumber, cue 4th acolyte, build graveyard then crypt, then back to mine, cue 5th acolyte, build zig, build alter, when crypt is done cue 2 ghouls, build zig, when alter finishes build your hero of choice death knight or dread lord. Either go harass or solo creep with ur hero and skeletons from wand. Soon as resorces allow upgrade to halls of the dead. When halls of the dead is done start pumping out those gargs. build slaughter house and get 2 statues. gargs are great because they can fly over trees for good harassment and they make great hit and run units.
My favorite undead strategy! Name comes from the fact that your heros will be doing most of the killing by coil/novaimpale on units, especially heros! There is no faster way to kill an enemy hero then to tri nuke them.
Best versus: EVERYTHING!!!
Build order: Same as dual aura only difference is your heros. First hero Death Knight, second Lich, and third crypt lord. You want to creep alot and fast at the begining because once you have lvl 2 death coil and frost nova heros/units will fall fast. Your main units will be ghouls simply because they are cheap effecient(especially with frenzy upgrade) and provide great meat shields. When u get into a battle look at the sinario to decide whether to nuke enemy hero or units. Nova and impale both can really screw over an enemies army as nova slows and does splash damage and if imale is done correctly you can stun a good section if not there entire army! The key to nuking a hero is doing it fast coil/nova/impale them as quickly as possible so that they lose a shitload of hp(if not all of it) almost at once.