Nie testowano, ale oto początek
return DB::table('phpbb_topics')
->join('phpbb_posts', 'phpbb_topics.topic_first_post_id', '=', 'phpbb_posts.post_id')
->join('phpbb_users', 'phpbb_topics.topic_poster', '=', 'phpbb_users.user_id')
->order_by('topic_time', 'desc')
->take(10)
->get(array(
'post_text',
'bbcode_uid',
'username',
'forum_id',
'topic_title',
'topic_time',
'topic_id',
'topic_poster'
));