The phrase "ere then" is an old-fashioned way of saying "before then". It can be rephrased with various synonyms depending on the context and tone of the sentence. Some possible synonyms include "prior to that", "earlier than that", "beforehand", "previously", and "ahead of time". These synonyms help convey the same meaning in a more contemporary and concise way. For example, instead of saying "I will finish my work ere then", you could say "I will complete my work beforehand" or "I will finish it earlier than that". More modern language choices can make your writing more engaging and accessible to your readers.