Tensei shitara Slime Datta Ken, Yondome wa Iya na Shizokusei Majutsushi Recommendations
- Both MCs are really strong / Get a lot of skills
-Both are somewhat like mascot characters, Rimuru being a slime and Vandalieu being a baby/child for a
- Both MCs build a country
- Death Mage is a bit darker
- Both have a nice amount of world building
These two light novels are both about the protagonist dying and reincarnating as a non-human in a fantasy world while gradually building their own kingdoms of monsters. The skills system in both series are very similar to each other.