When resolving the effect of "Pot of Avarice", the animation shows Fusion Monsters, Synchro Monsters and Dark Synchro Monsters as being returned to the Main Deck
Technically, there are two types of repack, Rudy told me
Karakuri Komachi mdl 224 "Ninishi" EARTH 3 [ Machine / Tuner / Effect ] This card must attack if able
Its no use having a pod of three people who want to experience a narrative and show off their cool thematic decks and pet cards, with one person who slams a combo in the middle of that story
Instead, you need two cards to combine them as one Pokmon in play (which also means that they are treated as two when they are knocked out, and thus your opponent gets 2 prize cards
During your opponent's Main Phase, if this card was Special Summoned this turn, you can (Quick Effect): Immediately after this effect resolves, Synchro Summon 1 Fish Synchro Monster using this card you control