I'll try to explain for my brother.
In the first week, he used Wyverns with the Castle faction.
He lost only one during the entire game, on the Angelite map.
A week before the final battle, he went to Utopia, and the Wyverns joined him.
P.S. He doesn't remember the exact number of Wyverns that joined, and he'll send you the approximate number in ICQ after the game, if he wrote it down at all.
Don't be harsh on my BROTHER - it's not nice.
And he has saves almost every week.