Luckamancy reserve is a special. Very little is known about it, but it seems to be the source of seafarer superstitions about double eagles. One double eagle in the WB2014 Duke Forecastle - Part 8 of level 2 has a capacity of 30 points, which it accumulates by causing bad Luckamancy or spends by causing good Luckamancy as part of the special.
It cannot steal Luckamancy from all luck related actions. The only confirmed way to charge it is through combat, though it has been charged by unknown means out of combat.
If the reserve is filled to capacity, it can bless a ship or a specific unit with a massive Luckamancy boost. According to Duke Forecastle, when the double eagle applied its blessing to him alone, it was as if he could do no wrong, though the effect only lasted a day.