Enchantment, BB (2) {B}, Remove two creature cards in your graveyard from the game: Put a 1/1 black Skeleton creature token into play. It has "{B}: Regenerate this creature." When Drudge Spell leaves play, destroy all Skeleton tokens. They can't be regenerated.1
Illus. NéNé Thomas
Destroys all Skeleton tokens from all sources if it leaves play. It does not just destroy ones generated by this Drudge Spell or just ones you control. [Duelist Magazine #9, Page 37]
The creatures in the graveyard are removed from the game during announcement and as a cost. [Duelist Magazine #11, Page 56]
The fact that Skeleton tokens are destroyed is an aspect of the enchantment and not of the tokens. Thus, only Skeleton tokens which are in play when it leaves play are destroyed. Ones which are going to appear due to use of the effect but which have not yet appeared are safe. [Duelist Magazine #10, Page 44]