Ogre King's Blood is a relic piece obtained from the Ogre King, the 2nd boss in the Cursed Forest. Alternatively, you can purchase it from the Adventure Store for 400 Smith Tokens once you have 4-Star Mastery in the Cursed Forest.
The other pieces you need to create Blood Etched Ogreblade are the 3 Rank-A Iron Swords; Silvermoon, Northern Wind, and Aegis. As you can see in the below picture, it will tell you how many correct swords you have. The below picture has none lit up with a gold border so no swords are correct.
Successfully fusing the 4 components together over 36 hours will result in your sword.