Mario Kart enemies

Hello, I own a server called QuantumCraft, and can't seem to find a plugin that fits my needs for this.
What I would like is basically enemies f0r the game, you are in a minecart by the way.
They are spawned by the command /mk spawn <name>
What I would like:
Thwomp - A slime that, when you are near, falls down from the sky (It must not fall when you spawn it) when it hits you, instantly die.
Koopa - A skeleton that instantly kills you (on collision) and also, it doesn't move.
Boo - A magma cube that does not fall and, when in a 6 block radius, slowly moves to you.
Bowser - A giant that every 6 seconds, shoots fireballs that instantly kill you and do NOT do block damage.

That is all, thanks Please make it 1.8 spigot.

 

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