WordNet sense 1 (brought together in one place):

gathered

WordNet sense 2 (brought together into a group or crowd):

congregate, accumulated, amassed, assembled, massed, congregate

WordNet sense 3 (gathered together or made less diffuse):

concentrated

WordNet sense 4 (in full control of your faculties):

poised, self-contained, self-possessed, equanimous, self-collected

WordNet sense 5 (serenely self-possessed and free from agitation especially in times of stress):

composed