Hydra, Shadow Assassin, Rot Beard, Spikey Dragon, Wild Satyr, Pole, Trio, Druid, Frost Giant, Dwarven Archer, Brozerker, Snap Dragon, Thief, Spirit Wolf, Plant, and Dracul all have piercing damage (Including only heroes from Server 9 at the moment)
Effective Aurum Piercing Damage heroes:
Hydra, Spikey, Dwarven, Rot Beard, Assassin, Thief, Dracul
Effective Aurum Piercing Support heroes:
Plant, Satyr (Can also deal heavy piercing), Brozerker
All other heroes on the list have piercing, but are usually not good for Aurum Stage 3. Maybe when his shield is down though.
Recommended Team:
Satyr, Bardbarian, Hydra, Dwarven Archer/Rot Beard, Spikey/Plant
If Hydra Legend, then Satyr/Plant, Hydra, Dracul, Shaman, Bardbarian
Or just a solid team would be at least two good tanks (If a tank is knocked back, Aurum will almost immediately start shooting random heroes with his pellet thingies), 2 piercing heroes/ 1 piercing and a bard, and maybe a healer if the tank of choice isn't already one.
Bardbarian is a good pair for the damagers. Orc Monk is good for shielding Aurum's attacks, healing, and tanking, Skeleton King's also a good healer and can summon practically infinite tanks. An alternate option to the solid team would be a tank, skeleton king as the healer, piercing, bard, and a heavy damage hero. This hero will widdle down Aurum's health when his shields are down. Remember not to focus solely on taking down the shield, for Aurum himself is the true foe you're supposed to kill.
Effective Damage Dealers (For When Aurum's Shield is Down) (Including heroes from other servers):
Pixie Queen, Shaman, Electroyeti if Legendary, Rabid Dragon, Rot Beard, Dwarven Archer, Satyr, Hydra (If Legend, pair with DoT like Dracul, Shaman, etc.), Bardbarian, Megataur, Thief (With stacking Basic Damage, after shields are down she can deal a hefty amount with her Basics [WHICH PIERCE!]), Bone Dragon, Understudy (Paired with good tanks, UU has low defense and health), Kaiju?, Unicorgi (Unreliable, Green Skill does immense damage, but it doesn't proc manually), Goblin Trio, Catapult, Genie (Low Damage, but paired with Bard, possibly could widdle down health), Vulture (Ehhhhh, deals good damage with special, possibly good green skill with Hydra Legend, but you'd hafta sacrifice a hero to make him viable), Spectral Drake (Actually no, this isn't good, I've tested Drake on Aurum, his spec insta kills him, but it glitches and crashes the game), Frost Giant (I personally do not know if his Legendary affects Aurum, but if it does, it may be worth it, but if not, then Frosty goes down the drain), Cosmic Elf (Only for a strong basic attack), Banshee (Stacking Death Fingers will destroy Aurum to bits as soon as his shield goes down).
Seems a little weird for me to just start immediately on Aurum 3 than rather scale it from Invokus to Venusia to Aurum Stage 1 - 3, but a guildie was asking for help on that specific stage and I couldn't help but budge my head in (Even though Ezio got it). I'd already written quite a lot on Aurum 3 after, so I decided to move it all here.
Legendary Skill quests and tiers come next!