How do auras work exactly?

[Cyberghost]

Hi guys, decided to finally try a paladin, and was looking at various guides and stuff, when i was playing over LAN with my friend, it occured to me that auras can only be active one at a time.
Now my question is, Whats the use in maxing out multiple auras, when you can only use one at a time? For example, im looking at a Hammerdin build at the minute, it suggests to max concentration, vigor and blessed aim. I thought awsome, better attack rating and damage, but then i quickly realised you can only have one at a time. So what is the use of having multiple maxed auras, when you can only use on at a time?

[SmittySixTen]

Blessed Aim and Vigor are synergies to Blessed Hammers. They will increase the damage quite a bit.

Right now I'm playing through the game untwinked with a Hdin and I'm gaining a little over 100 damage per hammer every time I put a point into Blessed Aim or Vigor. Keep in mind that this is with very low-end equipment. If my character was fully-geared with end game equipment, this increase would be much greater.

Concentration is the aura you will have active on your right ability square, and Blessed Hammers will be on your left. You will have to hold down shift in order to use your hammers effectively.

[ronya]

Attack rating from Blessed Aim does nothing for hammers directly, anyway, since it's a spell. The benefit from Blessed Aim is through the synergy - read the spell description for Blessed Hammer.

If you're just starting out with a Paladin... there are various caveats and exceptions with how synergies and auras work. Only skill points placed in Blessed Aim will increase Blessed Hammer damage: + to all skills, + to Paladin skills, + to Offensive Auras, and + to Blessed Aim will all have no effect on Blessed Hammer.

On the other hand, Prayer is also synergy to Meditation and Cleansing. But both hard skill points and bonuses from items will boost both Prayer's synergy to Meditation and Cleansing.

Basically the whole system is a complicated mess, so if you're wondering how a specific effect works, ask.