This is their organization, according to Monster Manual 1:You know that they get class levels too, right?
Solitary, gang (2–5), band (6–9 plus 35% Solitary or with tribe
noncombatants plus 1 adept or cleric of
1st or 2nd level), hunting/raiding party (6–9
plus 35% noncombatants plus 1 adept or
sorcerer of 3rd–5th level plus 2–4 winter wolves
and 2–3 ogres), or tribe (21–30 plus 1 adept,
cleric, or sorcerer of 6th or 7th level plus
12–30 winter wolves, 12–22 ogres,
and 1–2 young white dragons)
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For the most, they're just beefy brutes.In a whole tribe there are just one or two - mabye! - able to deal with something as simple as an Invisibility spell.
About the forgotten realm novel:
1. the young white undead was sent back to spread horror, no effort was made to hide the enterprise
2. I don't think that Forgotten Realms dragons are exactly standard d&d 3.5 dragons.