If your Olwen has a good spd IV you could pair her with Ninian and/or Brave Lucina and try to go for the quad strike on enemies. You could also put a Renewal 3/Reciprocal Aid set on Marth or Alm to heal and pass health to teammates.
I'd build a red horse unit- eliwood or xander and then take b!lyn, olwen(blarblade), camus and then red horse. Red horse and camus will be your hone and fortify cav buffs respectively and b!lyn and olwen would have goad cav.
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