Lore Guide to the prev. drawing
In Touhou lore, the Oni used to live on the surface, reigning over Tengu and humanity. They then decided to move underground by their own will once Hell was relocated. This drawing depicts an alternative world where they were forced underground instead.

Imagery:

The red hole is shaped as the head of an Oni, the single front horn with a star represents Yuugi, while the two horns to the side represent Suika. The Pyramid on the chain at the bottom also represents Suika, along with the broken gourds in the chin area. Breaking this chain frees the surface world from the Oni’s tyranny.

The red horns can also be seen as rivers of blood which originate from burned trees, which represents the destruction of the Tengu and their homes. The paper seal along the throat represents aid from the Miko (humans), which allows the Tengu to cut the Oni’s chains to the surface.

The spear is adorned with a Vajra symbol, symbolizing the properties of a diamond (indestructibility) and a thunderbolt (irresistible force). The bells on her ankles ward away evil spirits and help to call the Black Koi to her aid. Black Koi are associated with successfully overcoming an obstacle. In this case, it represents overcoming the Oni's oppression of the Tengu. The title of this drawing is "Banishing the Oni".

That is my interpretation, however all interpretations are equally as valid.
(Source: https://www.tumblr.com/ramnik5/669556902847463424/)