the part I've underlined is the problem as it can be read that even the character followers under the wizard's DI must be discarded, even worse - as far as I know it is accepted by most that it works this waySacrifice of Form
hero resource - permanent-event
Influence: +1
Prowess/Body: +1/+1
Description: Spell. Wizard only. All of the strikes from one attack against your Wizard's company fail; +3 to any body checks made to determine if the attack is defeated. Discard the Wizard (i.e., he becomes unrevealed) and any non-item cards he controls. Place any items he controls under his card and keep these off to the side (these items are considered to still be in play). If the Wizard is put back into play, return his items to him and place Sacrifice of Form with him. Wizard receives +1 to his prowess, body, and direct influence. May not be duplicated on a given Wizard.
obviously I do not agree with this interpretation:
First of all I think that character followers should not be treated as "cards the wizard controls", as they are not played on the wizard (like various events) nor by the wizard (like allies, items, etc.)
Secondly, the CRF and MEBA (the last and most up-to-date ICE made rules) say:
CRF wrote:Discard
- Whenever a character is discarded, all non-follower cards played with that character are also discarded.
so clearly when a character -who has other characters as followers under his DI- leaves play his followers aren't discarded, they just pop out of his DI (as it's no longer there since the character is no more) and move under GIMEBA wrote:Discarding Cards
When a card leaves active play (discarded, eliminated, returned to owner's hand, etc.), discard all cards played on it.
And thirdly - minion Arkenstone is a good example of how things should work, as there is no mention on it's card that character followers of the discarded dwarf should be spared - the CRF entry I quoted above handles that nicely.
Why did The Arkenstone get an errata is beyond me - probably just an extra, unnecessary text (like the 'site does not tap' bit on That Ain't No Secret - it's obvious that event's played on a site do not tap it unless it is said so in their texts')