The easiest way to check whether a card is legal or not is to look it up on Scryfall or Gatherer, where each cards legal formats are listed
It is a card that sees play in Pre-Modern
The deck is built to maximise the number of power-2-or-less creatures you can maintain, creating a damage clock that ticks up every single turn
Theres an easy way to build this commander with creatures that have death triggers, but unfortunately youre restricted to mono-black unlike with Teysa, which limits what you can do
I personally loved running it in Standard decks, and it was surprising how often the keyword soup came up as an alternative wincon
Mulan - Considerate Diplomat Super Rare Card 142/204, Sapphire Ink Another Princess from the Fabled set, "Mulan - Considerate Diplomat" gives useful card draw in a Princess-themed deck