Blood of Dragons (spoilers RotE incl City of Dragons)

['thul]

Many interesting ideas there...

theoretical ideas. Spoilers all books

It is indeed likely that nettle got herself entangled further with Tintaglia. Her attitude also befits an Elderling queen. Far more so than Malta ever did. The fact that she is also of the blood royal, will only enhance the facts. She is mature beyond her years, and has considerable power with the skill, which we all know comes from having Elderling ancestors. Fitz may be the skillmaster, but his education was spotty, without any draconic aid and without a true teacher. Nettle has all those things he did not have, as well as more time.

It is likely that the polearm is found in Kelsingra. There are none among the crew of the Tarman that have skill in using a forge, particularly on such scale. Considering that the rain wild traders have not been had any real warfare, there is no logical reason for them to have such skill either.
That leaves two possible sources. Trade and discovery.
Trade has three key sources. Six duchies, Chalced, Jamaillia. A weapon with such blade indicates war with ground troops and/or horse-mounted troops, not ships. the last has no known neighbors on the ground, so scratch that. Chalced would only want one thing from Elderlings/rain wild traders. Dragon parts. That leaves the six duchies, and they are generally too far away.
That leaves discovery. Kelsingra is right there, so source is very likely to be that place, or its neighboring Elderling cities.

The design on the blade resembles a glaive or a Voulge. Both were used for stabbing and, if hooked on the back, pulling riders off their horses. The glaive was utilized to slash, while the voulge was used for hacking. Both of those weapons can be easily used in ceremonial circumstances, since they are typically held in the hand, where swords are sheathed.