The Forgotten is Sylvain's Paralogue Chapter in Fire Emblem: Three Houses. This chapter takes place in Kingdom Territory, and is available on all routes during White Clouds after completing Chapter 6.
The Lance of Ruin was available to obtain at the end of Chapter 5, however Byleth could have returned it to House Gautier by choice. If Sylvain was not in Byleth's class at the time or they chose to return it with him in the house, the lance can be obtained at the end of the chapter.
- Energy Drop - Thief
- Magic Staff - Thief
- Speedwing - Thief
- Short Spear - Thief
- Goddess Ring - Thief
- Advanced Seal - Thief
If most of the thieves are defeated (more than half?):
- Large Bullion
Upon completion of the Paralogue:
- Battalion: Gautier Knights
- Lance of Ruin (if not already obtained following The Gautier Inheritance)
This mission will require you to split your forces to attack four different exits that the thieves can use to escape. Don't immediately go after the thieves that have items, or you will be hard-pressed to catch them before they escape. They move on turn 4 enemy phase. Take out the four enemy bandit leaders first before worrying too much about the ones that will drop items.
Each of the four bandit leaders will be equipped with an Iron Shield, which the player could optionally steal, but it is likely that the player will have access to Steel Shields at this point, so it isn't really necessary.
When engaging any enemy unit in this Paralogue, make sure to kill it quickly, as it will run for one of the exits upon taking any damage. The bandit leaders will not flee, though.