i think they might be one of the strageties in one of the booster packs
here are a few possibilities the ones with * i think he might have
DARK WORLD CARDS - found in EEN (elemental energy)*
FROG CARDS - some found in cybernetic and shadow of infinity
THE ELEMENTAL CHARMERS- some found in lost millennium and EEN*
THE ROCK CARDS- a lot found in lost millennium
DD cards- spread through out some booster packs*
SPELLCASTERS- found of course in the spellcasters judgement deck
there are more obivious combos in booster packs but if there are more tell me