I find it really funny that Victoria explains to us that boosting combat bolt from the start was a good idea... That's the only spell I upgraded because I didn't want to have 50% of mu turn spent using a skill I didn't upgraded and was doing 0 damages... Combat bolt every turn is good X)
I use both "combat bolt" and "rictusempra" in duels.
I hit them first with the "combat bolt" then in the next round I use "rictusempra"
this does medium damage but also (can) leaves them stunned so they can't hit back,
then just repeat, doing this means that I hit them twice for every time they hit me,
BUT also they can Only use "combat bolt"
because every time it's their turn to use a Level 2 spell they are stunned and miss that turn.