Soul has to eat 99 souls and one witch to become Death's scythe, and souls don't taste of anything. Soul Eater just likes the feel of them going down, swallowing them. Soul has a large scar across his torso that he got saving Maka. The scar was from the demon sword Ragnarok wielded by Crona.
After the battling with them, he was put in hospital, Soul has been having nightmare's about jazz music and a little red devil like demon who does not seem to dance with the rhythm .
Another parts of the dream is that he seems to be bursting out of Maka stomach, Soul has a small trace of black blood given by Ragnarok and Crona in the battle, The blood has started to infect Soul body and mind.
Soul is best friends with Black Star and in one of the episodes Black Star was going to become partners with Soul and they tried to fight Death the kid but soul and black star could not fight due to differences of wave length between there souls. Also the only way they were able to defeat Death the kid was because he had a nose bleed, soul cut the kids hair out of symmetry in a disorderly fashion leading to his obsessive-compulsive disorder flaring up.