Here is a Cronous Mage Build I collected from other website , if you are planning to build your mage , you can read the following information .

STAT:

Many cronous cro  players choose to put down a little bit for stamina, but your armor and accessories should provide you with enough hp and def to keep you going at your lvl. The draw is, mages are poor on attack side, so we need to do whatever we can to get this INT as high as possible.
As such....INT jade of Aiur (or Etner Karis which already has INT built in), will do much to further the attack of the mgae.

SKILL:

basic

1 pt weight
MAX shield mastery
MAX staff mastery
1 pt health recharge
1 pt mana recharge (but id suggest highly to add pts here when you get extra)
1 pt dodge

class

1 pt magic shield (my bonus gives me over 70% worth of magic shield....so anything higher would be bad for me)
1 pt mana compress
1 pt teleport
1 pt ice (useful for slowing and THAWING mobs when they are stuck)
MAX astral (my main attack during non xform)
MAX lightning (very useful when needed to target just one single monster in a mob)

lvl 90 skill

Same here...astral and lightning all the way....

I know many sub 90 mages are really really looking forward to unlocking their lvl 90 skills.
Im REALLY REALLY sorry to say that most of the lvl 90 skills are quite worthless at this time.
The lvl 90 skill take up a HUGE amount of skill points, but do not deliver on their cronous cro ...

Lets take absolute fire for example...

Takes ENORMOUS amount of time for recast and has a VERY small radius.
It maybe good against 3-4 monsters at TOPS, but thats all its good for.
The dmg is SLIGHTLY higher than max astral (at lvl 30 astral, when I last checked....)
But at my lvl 40 astral (which is the MAX u can get), it is probablly HIGHER than absolute fire, ..casts 3-4 times FASTER than absolute.
Also, the extra 1,000 pt fire dmg....NOT worth it against monsters....only effective against other cronous cro  players in pvp.

How about Glacier Prison?

Ummm....dun even think about doing any type of dmg with this skill...it is quite ugly.