“ A casual remark by one of the party about something met on a previous adventure leads to a summons to and grilling by the Mages' Guild (or equivalent), probably resulting in an expedition back to that area to recover the things for study by the Guild. The party's presence will be 'requested' for this expedition.”
“ A weapon of war created by an extinct race, this rat appears normal but is a simulacrum - beneath it's mangy fur is a body of bronze. Commanded by words in a lost language, wherever it goes a virulent and lethal plague follows. The cure is similarly obscure.”