Morii Shidzuki uploaded onto Twitter the full-body illustration for Ereshkigal Alter as she appears in Fate/Grand Order. She appears in the story of Lostbelt 7, as well as in the animated commercial which aired shortly after the second half went live on the Japanese server. Aside from a different outfit and a more Mesoamerican weapon, Ereshkigal Alter strongly resembles her normal counterpart.
You can check out the full illustration here:
FGO 第2部 第7章「ナウイ・ミクトラン 惑星を統べるもの」にてオルタ化したエレシュキガルを描かせていただきました～どうぞよろしくお願いします pic.twitter.com/NMcgZeIr2v
— 森井しづき (@forestman) February 7, 2023
Ereshkigal Alter does not appear in the game proper as a separate Servant. After you complete Lostbelt 7, you will be able to unlock this outfit as a Costume Dress for Ereshkigal. Technically speaking, Ereshkigal Alter does not refer to herself as such in-game. She calls herself Ninkigal, which is not a reference to any existing deity. It is likely a pun that uses ‘ninki,’ which is the Japanese word for ‘popular.’
Lostbelt 7, which is the South American Lostbelt, is the final Lostbelt in Fate/Grand Order Part 2. The second half of it (which introduced Tezcatlipoca, Tlaloc, and Kukulkan as playable Servants) launched in late January 2023. Again, this is only for the Japanese server. The global server, on the other hand, is counting down for the British Lostbelt, which is Lostbelt 6.
Fate/Grand Order is readily available for mobile devices.