Abilities
As with all characters in Odin Sphere Leifthrasir, be sure to get Recovery Up, Charge Up, and Power Supply to keep your HP and POW up. For Mercedes, the next ability you definitely want is Keep Away. This will allow you to knock back foes with just regular shots, giving you time to reload if you need to.
Ground Attack isn’t really necessary if you’re always in the air, but you’ll need to unlock that if you want Aerial Defense, which decreases your damage received by 30% while in the air. Full Power is another good ability to have, as you’ll be more likely to knock back foes when your POW meter is full.
Your priority as Mercedes should be to get the leftmost abilities on her skill tree. Reduce Damage is invaluable as it will decrease your damage taken while reloading by half. The final leftmost ability, Quick Reload, will increase your reload speed, which is a crucial one to have because you’ll run out of regular shots very quickly.
