If it is a monster, he can Normal Summon it immediately
I wouldnt have played Ancient Box if I didnt bring the top 20 decks in format stored in my couple of Omnihives that I have from Ultimate Guard which you can check out here
There are a few main differences between Standard and Pioneer: Standard rotates annually and Pioneer doesnt rotate at all
First Penguin has added more consistency to WATER decks, as you can discard 1 card to reveal 1 WATER Synchro Monster in your Extra Deck and add a WATER monster from your Deck to your hand with the same Type but 1 Level lower
Removal interacts with mutate spells strangely If your opponent casts a creature for its mutate cost and you remove the creature it was mutating onto, the mutating creature spell doesn't fizzle
What made this deck so dominant during its peak was the fact that just a single Zoodiac monster was all that was needed in order to summon one of the archetypes many Xyz monsters, rather than the typical requirements for two or more monsters of the same level needed for other Xyz monsters