Welcome to Librarium Online!
ok so my set up on a old blood is
Sword of blood shed (+3 attacks)
which after he has done a wound will give him 9 attacks
ok so now on to magic with my slan useing it on the old blood would it be best to go for light with the number 2 spell WS 10 I 10
or go for beast and cast the number 5 and signatuer spell on him giving him + 4 attacks + 3 str and + 1 toughness makking him toughness 6 with 13 attacks and str 8 this is the one which i dont know is legall can he have more then 10 attacks?
If it's a buff then I'd say that it's legal, or if it isn't...
I see that as the correct interpretation of spells that allow targetted infantry models to morph into mighty creatures, they literally lose all their magic items in the duration that the spell is in play, think about it one of your tooled up characters had turned into a dragon, would you actually see such a mighty creature (60-80ft tall!) carry a magial weapon in one of its hands, or wear a suit of magical plate mail? I don't think so.
Tha Slann for example with it's Disiplines, these are special rules for the Slann, which means that you can make him Ethereal and have him in the form of a dragon! An Ethereal Dragon! . That you can probably get away with as the Disiplines are upgrades for the Slann not Magic items
So to answer your question, the Oldblood's set-up is good, as far as I know you can't keep those benefits when transformed into a mighty creature, unless they are magical buffs you can .
Hope this helps!
Legally I think you can have more than 10 attacks. Any thing in your stat line can't go above 10. But the weapon and things don't change your stat line, they just add attacks. There is a slight difference there that will allow it.
I am right 94% of the time, why worry about the other 3%.