Summarizing...
Eldritch Breath (Su): A demon drake may blend baleful magical energy to impart additional debilitating effects to its breath weapon. Each of these additions may be used three times per day. Eldritch breath effects affect anyone in the area of the breath weapon, and victims must save separately for the fire damage and eldritch effect. Only one eldritch breath effect may be used at one time. Eldritch breath is treated as part of the breath weapon for purposes such as metabreath feats (see Draconomicon).
A juvenile or older demon drake may beshadow its beath weapon, blinding foes for a number of rounds equal to its age category unless they succeed on a Fortitude save.
A mature adult or older demon drake may bewitch its beath weapon, confusing foes (as the confusion spell) for a number of rounds equal to its age category unless they succeed on a Will save.
An ancient or older demon drake may befoul its beath weapon, sickening foes for a number of rounds equal to its age category unless they succeed on a Fortitude save.
A great wyrm demon drake may besmirch its beath weapon, nauseating foes for a number of rounds equal to its age category unless they succeed on a Fortitude save.
Enlarge Breath Weapon (Su): Three times per day, a wyrmling or older demon drake may enlarge its breath weapon, thereby doubling its radius.
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