blood eclipse

You only have 20 units of blood 

You roll a D20 to see how many units of blood it takes to create it 

for example :

At level 1-5 you can only roll under 7, if so it works but if its higher it fails but you still lose the amount of blood 

At level 1-5 roll a 7 or under

At level 1-10 roll a 10 or under 

At level 1-15 roll a 13 or under

At level 1-20 roll a 19 or under 

You can control your own blood.

Its only limit is your imagination