What is a grey seer?

[Pink Eye]

Also, is lighting their only power?

[Gobbo Slayer]

They are the Priests of the Skaven society and praise as well as spread the word of the Horned Rat, they have tons of influence and power in the society.

http://warhammerfantasy.wikia.com/wiki/Grey_Seer

They posses lots of magic power too and can draw lots of spells from the Lore of Warp.

http://warhammerfantasy.wikia.com/wiki/Skaven_Magic

[Grimmrog_SIG]

it is heresy

[Jakal, Lady kisser]

ratty priest with magic spells. they have lots of magics but a lot of them REALLY like the "kill everything with evil lightning" one because that'll show 'em.

[Touch Me]

What is this talk of Skaven or this Horny Rat thing? There is no such thing, just a myth to scare children to bed and obedience. Nothing more, nothing less.

[Teddy]

#skavenjustamyth