Not sure about how card text works in the dead pile. Does the text on Knight of Summerhall mean it can be played from the dead pile or is another Knight of Summerhall meant to pull another one from the dead pile into play?

Card with their own name on it refer only to that copy of the card (see Self Referential in the FAQ) - so this is one case where the ability specifically allows you to pull Knight of Summerhall from the dead pile.