Buff Knight Advanced

You can find dragons as the bosses of stages 9, 10, 11 and 12 (with 11 being the easiest in my opinion). Obviously you will get four from finishing all of the stages, so you just need to go back and defeat six more by replaying any of those levels and killing the dragons at the end of them. Also, as you play through the later stages you will encounter smaller dragons as regular enemies but these do not count towards this trophy, only the boss ones do. Once you finish off your tenth one the trophy will pop.