Sidar Jabari of Zhalfir

Sidar Jabari must be on the battlefield or in the command zone at the moment you attack with one or more Knights and also as the triggered ability tries to resolve. Notably, if Sidar Jabari is on the battlefield and its eminence ability triggers, but it's put into the command zone before that ability resolves, that ability won't do anything as it resolves. This is because an object that changes zones is considered a new object.