Great work!
I love how simple this is. I also like the graphic design, and how you've woven just a hint of the game's lore through the sheet- That's super cool!
I do have one concern however (without having played it yet)- it seems like the Attack vs Defence maths is off. I assume Attack rolls have to exceed the target's Defence to cause damage, but it seems VERY unlikely for that to actually happen. If I've done my calculations correctly, the average Attack roll is about 7.5. while the average Defence score is 15.