540 Cube Thoughts?

Unexpectedly Absent (W)
Day's Undoing (U)
Whisperwood Elemental (G)
Magus of the Library (G)
Boreal Druid (G)
Selesnya Charm (GW)
Mizzix of the Izmagnus (UR)
Broodmate Dragon (BRG)
Rith's Charm (RGW)
Sedraxis Specter (UBR)
Odds // Ends (URW)
Hide // Seek (RWB)
Seal of the Guildpact (CL)