Hola!

I'm concidering also making a pure mage (with cloth), and I like the necromancer-type from other games.

What I had in mind was going in the Conjuration tree, max out "cast XXX level conjuration spell for half magicka", and max out the left side of the tree, for atronachs.

I find it fitting to use destruction magic, and focusing manly on ice-spells, (necromancing = ice cold) for the paralysing effect, and go for dualcasting here as well, for a staggering effect. Paralyse + staggering = win?

I also figured I'll go up a little in the Alteration tree, for the 20% block of spells (x3), and the mage armor (x3), for some passive effects.

Restoration for 50% magicka regeneration, and the necromage, for more dmg against undead (Skyrim is LOADED with undead) However, it doesnt say HOW effective the spells will be? Anyone tested?

I also have enough points to max out Alchemy.

Will also put some points in Enchanting, to get the +25% frost enchantments.

Thoughts/inputs?

Sounds like an interesting roleplay, you got a backstory in mind? Also, this build screams The Ritual Stone.

Can you enlighten me what the Ritual Stone does? I can imagine its something for my conjuration spells?

It has no backstory, really. Just that Ive been playing Age of Conan, and I had a necromancer there, who had a lot of ice-spells and so on.
But its also what I think about when I hear necromancer, its cold as the death it self.

Heres the build:

http://www.ign.com/builds/the-elder-scrolls-5-skyrim?d=00000000000000000000000000000001211111100011111002100111101110110000020010131111035111111110000000000000000000000000000000000000000000000000000000510001111

That requires a LVL of 64, and Ive used all the points I think is necacerry.

Any thoughts of where I should put the rest of the perk-points?