The fact that you have to tribute a monster for it, or waste a Special Summon (Mystic Tomato for example) just to pack a 900 punch
You lose out on mana efficiency with this motherly Phyrexian but gain so much
Sure, you can treat her like a repeatable X spell, but you'll quickly run out of mana, and that mana would be better spent elsewhere
Any three of these 10 cards: Shiny Charmander Shiny Charmeleon Shiny Dondozo Shiny Kakuna Shiny Pachirisu Shiny Revavroom Shiny Riolu Shiny Varoom Shiny Weedle Shiny Wiglett Shiny Museum 4 This time, there are not four Shiny cards, but youll have to collect at least one Shiny super rare card
Read all about mulligans, sideboarding and most importantly: How to sequence your turns
But they both work perfectly in combination