Hi I am the Tougen Anki Oni technique generator give me an idea and I will expand on it and give you a technique

Ex: blood spikes

Name: blood spikes

Description: If user cuts themselves they can harden their blood like spikes, knives, spears, ect and throw them at the opponent. If user is in full Oni then they are stronger and faster.

Drawback: If user takes too much blood too quickly they can pass out