Polkacloud

"???" Elements: Shadow, Mech, Poison, Spectral

This monster can be bred with two Double Elements.

Arackulele + Googlug

Shadowmorph + Dragong

Kazilleon + Drummech

However, it can be bred with a Single Element and a Triple Element.

Frogget + Grumpyre

Didgetiki + Reebro

Sitarthon + Humbug

Skulltar + Spectgon