What strange gift does the Steersman bring for Paul? What do you think the true intention of this gift is?

The Steersman brings a ghola, a clone/re-incarnation, of Paul's old friend and mentor, Duncan Idaho. The ghola is most definitely intended to destroy Paul, as this was revealed in previous chapters by the members of the conspiracy. However, Paul senses an honest decency in this ghola, and perhaps enough of the real Duncan remains for the trap to be avoided.