Emry occupies an interesting spot for a threat, mostly because shes actually hard to kill with Fatal Push (since revolt isnt a given like it is in Modern)
Something similar to Ingest, for example
At the beginning of each combat phase, we get a 2/1 Myr artifact token, after which another token controlled by ourselves may be selected, from which all other tokens become copies
At a certain point, when there is enough mana available on your board, you can get a (fairly) safe win with the 3/1 XRGW Elf Rocco, Cabaretti Caterer or go infinite with the right combination, for example Kiki-Jiki & Conspicuous Snoop, Temur Sabertooth and Zacama, Primal Calamity, or Vizier of Remedies and Devoted Druid
She ensures that +1/+1 counters do not disappear when creatures leave play, which reduces the impact of removal and board wipes while increasing the importance of stable mana access through the top dual lands in MTG