World of Conquest (暗夜の世界, Anya no Sekai lit. World of Dark Nights) is the second chapter of Book I of Fire Emblem Heroes.
The names of the five parts of this chapter are Conquest Trial (暗夜の試練, Anya no Shiren lit. Trial of Dark Nights), Lovely Bloom (可憐な妹王女, Karen na Imōto Ōjo lit. The Lovely Younger Sister Princess), Callous Prince (冷酷な弟王子, Reikoku na Otōto Ōji lit. The Cruel Younger Brother Prince), Bewitching Princess (妖艶な姉王女, Yōen na Ane Ōjo lit. The Seductive Older Sister Princess and Prince of Conquest (暗夜の王子, Anya no Ōji lit. Prince of Dark Nights).
Part 1: Conquest Trial
Subjective: The following part of this article is based upon the editor's personal experiences and opinions, and therefore may not be applicable for all readers.
Xander lies in the top of the island waiting for your units to reach his attack range. The best way to defeat him is to send either Blue Tome unit or a Lance unit up North to the bridge.
Then, send your Blue Tome unit to the bottom bridge in order lure Leo and Elise to their attack position. When your next Player Phase begins, attack and defeat Leo and Elise.
Also, if you have an Archer unit, a Sword unit, or a Red Tome unit, it should be easy to take out Camilla if you can reach her.
Part 2: Lovely Bloom
Watch out, Effie is an armored Lance unit whose attack and defense power are higher. The only way to defeat her is to use your Green Tome Unit or your powered-up Axe unit, especially if your Axe unit has a Hammer weapon.
The best strategy to reach Elise and an Emblian Troubadour is to send two of your units to break the walls inside the fortress. Once you dealt with Effie on the left and Arthur on the right, take out Elise and an Emblian Troubadour before they heal to one another.
Part 3: Callous Prince
To take out Niles, you must send your powerful Archer unit, Tome unit, or Thief unit to the right side of the map and attack him on his range. To take out an Emblian Red Mage, send your powerful Lance unit or Blue Magic unit to the left side of the map to distract him.
Remember, Leo is a Red Cavalier unit and Odin is a Blue Mage unit. If you have an Axe-wielding Wyvern Rider and if you defeated Niles beforehand, take out Odin as his defense is lower than his resistance. Also, Leo is a cavalry unit and can't traverse through the forest tiles that well, so your units can be safe from his attacks for a while. But other than that, defeat Odin with your Lance unit or your Blue Tome unit.
Part 4: Bewitching Princess
Move your Lance unit or your Blue Tome unit to the square right before the right bridge, that way it can lure Selena in range so you can take her out. Be sure to keep your Axe unit or your Green Tome unit on the back of your team from Selena, you might need to keep them alive in order to take out that Emblian Lance Flier.
When both Camilla and Beruka fly forward to the front of your team, defeat them both with your Archer unit, your Sword unit (if you can reach them), or your Red Tome unit.
Part 5: Prince of Conquest
The map is basically an arena. The easiest way to take out Peri is to use your Axe unit to lure her into her attack range, that way you can defeat her at ease. Be aware that the other enemy units can charge forward.
Once you dealt with Peri, defeat Xander and Laslow with either your strong Lance unit or your Blue Tome unit. You should also defeat an Emblian Axe Cavalier with your own Sword unit or your Red Tome unit. Remember the weapon triangle and it should be easy to clear this stage.