Warrior Realm (Kingdom of Warriors in the Japanese version) is Chapter 3 of Fire Emblem: Awakening.
This chapter is not too difficult, though misplaying your units can be brutal. Firstly, have Chrom speak with the NPC Kellam to add him to your ranks. Kellam's high defense rating allows him to lure in the archers to the left so your units can ambush them. The soldier may also attack Kellam, so an Axe or second Lance user could be of use.
To the right, send Sumia, a cavalry unit, and two others to attack from the right. Since all of the archers are planted at the left, Sumia can wander in the right without getting picked off by archers.
When proceeding to the stairs, position a unit like Vaike or the Avatar to be ready to take out the Knights. Once they are gone, sword users, like Chrom and Sully, can handle the Fighters and Mercenaries that approach next. Once they are all gone, all that remains is the boss. The boss has similar weaknesses to the other two Knights, so magic is particularly effective at defeating the boss, as well as Axes from Frederick or Vaike. You can get a Hammer from one of the fighters that Frederick or Vaike can use to easily defeat Raimi. Once the boss is defeated, the chapter has been completed.
This is arguably the toughest chapter in the game in Lunatic Mode. There's no guarentee that you will survive, and even less of a chance that you can do so without having some martyrs.
This is the strategy that I personally reccomend, as it lessens the death toll that tends to rack up on this level.
Take full advantage of the battle preparation screen to view your enemies. Check what they're holding carefully, along with their attack stats (as there are no mages on this level, thank god).
On your first turn, have Chrom run over to Kellam, recruit him, and then run back out of the range of the archers. Moving out of the ranges of the knights is not completely necessary (because Kellam is a decent knight and Chrom has Dual Strike+) but reccomended. You should then push all units to the west and have Frederick kill off one of the enemies (preferably one of the archers, if possible). Keep your other units out of direct fire from the archers and knights, and you should be fine.
The enemies will swarm your forces, especially the archers. If you haven't killed off one of the two archers on this side by now, then there is no guarentee that Frederick will survive the beating that he can (and probably will) recieve. The other units from the east will come from behind.
Have every unit besides Frederick defeat the weakened enemies. It should be decently easy, assuming that you use either your Avatar or Miriel to defeat the knight. The archers are easy to kill, just swarm them with units who can attack the archer from one space away. These archers don't have Pass, so just keep units out of their range so that they can't move at all. Have Frederick heal if needed and then charge the east units.
The archers (if they're still alive) can't move at all, so they aren't a problem here. The enemies from the east, however, are another story. They probably won't defeat Frederick, but they'll bring his health down significantly. Other than that, this is pretty straightforward.
Have whatever weak units you have finish off the archers. If they are already dead, then begin bringing units to the east and assisting Frederick in finishing off the weakened enemies. With proper placement and a bit of luck, it is completely possible to defeat all of the lower enemies this turn. As long as you take out both the enemy knight and the archer, then you should be fine, whatever the outcome.
You should now have two door keys. Go up through the west doorway, and have any unit other than Frederick open the door. Trade items if necessary. Make sure to send your units in one large group, as trying to swarm from both sides ends in failure due to the hammer barbarian on the east side. Defeat the knight at the top of the steps.
All of the enemy units besides Raimi will charge your units. Assuming that you kept your units out of enemy range, that's really all they can do.
You must kill the hammer enemy this turn. No exceptions. The alternative is to waste Frederick's turn by having him hide from the enemy, and probably losing a unit to the other barbarian and the archer. I achieved this by having Miriel and the Avatar snipe it with spells, and then had Frederick equip and iron sword, pair up with Chrom, and attack it. Have your remaining units surround the archer as usual. We don't want him rampaging around.
The final knight can't reach you in one turn, so have fun watching it blindly run into your range. You can either snipe it with Miriel and the Avatar, or you cna simply use Frederick's newfound hammer on it.
The boss, Raimi, wields a short spear. The simplest way to defeat her is to use Miriel's fire tome, the Avatar's thunder tome, Chrom's rapier, and Frederick's hammer in quick succession. This way, your lesser units can gain experience.
- If Kellam is left ignored for a few turns, he will start wondering why no one has seen him yet.
- Humorously leaving Kellam alone and not speaking to him will cause the enemies to ignore him completely as well. However, this can be an advantage to exploit so that he becomes a wall that will not be attacked until the player opts to talk to him with Chrom.