Hm... maybe four or five high powered spells? Like, that ice took probably as much energy as it might take me to get up and walk across the room. I wouldn't notice the expenditure, right? But like... if I wanted to make a big -- or just more powerful damage-wise -- reaction, it'd be tiring. My magic energy and physical energy seem to be separate in a way, but in the end they both draw from the same pool.