Who to give Flame Blessing to?

Sigurd for the memes and for the nice cavalry synergy.

I'd recommend Sigurd as well. The defense boost from legendary Ephraim will help him tank even more, he can also give legendary Ephraim Calvary buffs as well as receive buffs from him. Plus, with his red color and default skill set, he excels at tanking green mages, which are units that legendary Ephraim struggles with due to his middling speed and subpar res.

Me. I need the defenses.

....JK. Sigurd for sure.

Sigurd would be the best one. Horse Emblem op.