NPCs and Clever Tricks
Cruise the map (very frequently) hiring all the NPCs that are even remotely competent. You do this particularly in the opposing country. You leave the NPCs in fiefs of the other country, particularly ports and inactive fiefs (where players tend to go offline). Then you check (via the NPC aborted Kidnap) who is in those fiefs on occasion. This is pretty time consuming. It is a natural job for one (or both) of the national heralds.
What this does is;
1- Sops up all the NPCs that the other side needs as bailiffs etc. If your side needs them you pass them out to your friends (and NPCs are one of the best "coin" to pay favors, spies, traitors-effective, appreciated and untraceable)
3- You can spy into lots of fiefs (I found all sorts of people this way in Three)
3- The one who has to counter this is usually the enemy King (since he is the one who can seize all over) so you spend some time planting NPCs quickly and the enemy king (a very busy man with lots to do to make his team run) has to burn an hour trying to get NPC seizers there and trying to grab them.
The two national Heralds, if each get 100 NPCs, can put a serious dent in the NPC pool for the enemy.
What about the expense? Whoever does this should be someone with a high family expense and a good size income to absorb the expense of maintaining all these NPCs.
Also, as the enemy King seizes the NPCs (maybe 100 or more in the course of the game) they "vanish" from the game in to the black hole of the King's Dungeon.
This is a neat use of Seize:
The King can seize anywhere in his country, but only in a fief where he has an NPC. Active players, particularly the National Heralds, should seize a supply of the King's NPCs (preferably those with decent Seize ability).
Then when the player comes across an offline enemy in a fief he leaves one of the king's NPCs and leaves an online message to the King to bag the invader in Fief XXX00.
This works better for the invaded power (generally France) than for the Invader.