Not hard to see why with such a fantastic ability: when Synchro Summoned, you can banish a card from your opponent's field, Graveyard, and a random one from their hand
The mill variant is just the top deck compare to Dimir tempo, both the regular and Lurrus versions
The equipped monster's ATK becomes double its original ATK, also if it attacks a Defense Position monster, inflict piercing battle damage to your opponent
Having a significant portion of a set's value concentrated in what essentially amount to foil mythics in terms of rarity makes opening boxes and packs an extreme gamble for the average player, and this had lead to some complaints
SE Secret Rare Terra Firma Gravity X TRAP During your opponent's Battle Phase, if you control "Elemental HERO Terra Firma": This turn, all Level 4 or lower monsters your opponent controls that can attack a face-up "Elemental HERO Terra Firma" you control must attack it, and cannot otherwise attack