Silly Noob Question regarding Lightless Lanterns

[Hector, tamer of horses]

Hi Guys

I have read many of the excellent strategy guides on this site. There are so many and they are so good, where do you guys find the time to write them?

Anyway, when boosting research capability, the use of "Lightless Lanterns" always comes up. Why, my noobishness asks, would you choose Lanterns over "Skull Mentor" (which provides 9 extra research in place of 6 for Lanterns). I have had no real difficulty collecting Death magic (admittedly I have only played T'ien Chen, Agartha, and Abysia) and these Mentors translate into a massive increase in research capability. Why would I take a %50 cut to have Lanterns?

Also, it appears that you cannot use two Mentors on the same guy (for an RP bump of 18). Why is that? Also, can you add a Lantern to a researcher that already has Mentor for a cumulative bump of 15? I guess as a side question, can you used two Lanterns on a researcher for 12 added RP?

And a last question, I have only played SP. I really enjoy T'ien Ch'i. So very flexible. But from what I have read, they get massacred in MP because the bless nations take them down fast before they can get rolling. Is this so? Is there a way around this or are they just dead out of the box? Don't really have the time for MP so I can't really find out for myself.

Thanks, in advance.