mtg rune cards Rune-Tail, Kitsune Ascendant // Rune-Tail's Essence [Saviors of Kamiga it has Equipped creature gets +1/+1 and has trample. Rune - MTG Wiki

It first showed up in the IDW comic The Spell Thief

She was designed to team up with one player by giving them a lot of Hippos, use them to attack the other players, and then steal all the Hippos back once its down to one on one

It pairs particularly well with Mox Amber from Dominaria , which is not only a zero mana artifact that Sai enables, but can also be sacrificed by Sai when you draw multiples

This archetype is really cool and flashy and theres a lot of room for further innovation

This archetype seems to have only emerged in the past couple of weeks, but has gone from strength to strength, steadily becoming a larger part of the Modern meta