This page contains the following information.

E	E	E	E	E	E+	D	E	E	E	E

Learns Waning Shot upon completing budding talent.

Mercedes starts with D rank faith, and is the designated healer of the Blue Lions House.

When playing the Blue Lions route, her faith rank at the beginning of the game is inferior to both Linhardt & Marianne who have a D+ faith rank. Therefore, the earliest possible time she can get Physic is in chapter 3. Physic is accessible by Chapter 3 without lectures, but her goals must be set for Faith only to get 1.5x growth, to favor lectures on other units. Players on Maddening (no NG+) would be stuck with only 5 uses of heals for Chapter 2, which is a long chapter, and forces the player to carry Vulneraries on every unit. In comparison, Linhardt & Marianne can reasonably reach physic in chapter 2 for 8 uses of healing spells instead of 5 that Mercedes have. Though Mercedes gets Physic in chapter 3, it's only 3 uses compared to the 5 that mission assistance Linhardt & Marianne will have. They will also have a larger range than her as they are level 5 when asked for assistance. She can be easily replaced by them once out of house units are recruitable in intermediate classes. You can feed kills to her to increase her level, but you do so at the cost of training better combat units.

In House Mercedes does have a unique feature to her in that she provides Might to Annette. At A support, they give each other +3 Might. If the player wants to use Annette, it can be worth using Mercedes as an Adjutant to a unit to reach level 10 for Pegasus Knight access if one wants to make Annette a Wyvern Lord wielding Bolt Axe. If Annette is not going the Wyvern route, Mercedes does not need to be leveled. In Chapter 13, Annette & Mercedes are in danger at their starting point, however that doesn't mean you have to train her. There's a skip solution that you can do with Stride & Impregnable Wall equipped on them on a Byleth that's a flier. Getting Mercedes to level 10 can be nice as well for her paralogue to fly her out of danger. She's not really in any danger if she's not a flier if the map is able to be cleared at a reasonable pace. Linhardt is desirable to recruit as one of the three users of warp excluding DLC. The warp range may be low, but you take any you can get.

Out of house, mission assistance Mercedes does not have Physic until chapter 5. She becomes a better unit to recruit starting in Chapter 6, which is when recruits are in intermediate classes. It might be better to wait and recruit her in chapter 7 if you want slightly better stats and higher level. The large Physic range for an out of house recruit is nice for a route map like chapter 7. She can also instantly class into Pegasus Knight for her paralogue if you're not planning to use her long term as well.

In the Golden Deer house, Mercedes can replace Marianne as a dedicated healer, and Marianne can become a dancer. Marianne makes a good dancer for the Golden Deers because of her Riding boon and starting position in Hunting By Daybreak. If you do need healing, you dance your healer, not use your dancer to heal.

In the Black Eagles house, though her paralogue that she shares with Caspar does not exist post timeskip, she is very desirable to recruit for providing Might as an adjutant to Jeritza, who is a very strong unit.

Mercedes can build support with the following characters.

Mercedes will automatically be recruited if the player selects to teach the Blue Lions house.

Mercedes can be recruited once Byleth has achieved a stat of Mag 15 and Skill Rank C in Bow. These requirements can be lowered if Byleth builds support with Mercedes, as shown in the below table.