Baby Slime

"Greater Summon!" Adrian casted towards the soul stone and it activated perfectly without failure.

[You have successfully summoned a Baby Slime.]

"Greater Seal!" Adrian casted.

[You have successfully sealed the Baby Slime.]

[Do you wish to name the newly sealed Baby Slime?]

Adrian thought what to name the slime and he found the perfect name.

"Dodu! I will name you Dodu." Adrian stated and the new monster successfully became his soulbound.

One would have doubts on employing slime as a soulbound but not Adrian because the Baby Slime he summoned is different. It had a clear golden soul which means that it could grow into a powerful monster if raised correctly.