Best Servant to face Lion King

Run Mordred & Siegfried back to back. Or you could borrow a Jalter for her extra "Dragon" buff, but I think Mordred is the far better option.

Both Siegfried and Mordred are uniquely cut out for that level, they both have raw defensive buffs (and light heal in Siegfried's case) & decent HP pools to boot. As you already know, they'll both return uniquely buffed damage right back at Larturia. Bring your Mash & a Waver if you are lucky enough to have one... since evades and invincibility buffs are useless in this fight, you'll wanna stack those DEF Buffs to the clouds Tituria jumps in to.

Though they are both AOE, I think they'll be your best bets, especially if you have already invested in your Siegfried.

P.s.- I've also heard Mephistopheles (upon completion of his strengthen quest) *might* be able to save you with a 3 turn buff block... that is if you are one of those people who liked him enough the level him this early in the game. Just a thought, I dont know exactly how viable it'll actually be considering her magic resistance.

mordred will do better than MHX;you know lion king is a lancer mordred has class advantage + np(deals heavy damage to altria) so mordred is good boi

Siegfried alone will do just fine, but you need to level his 3rd skill. You can bring a support Mordred for insurance.