
First level spells, weaken, clumsy, feeblemind.
if you cast one of the 3 on a target already under the effect of the spell:
1 your spell it's supposed to fizzle.
2 your spell use reagents.
3 your spell use no mana.
4 even tho the spell fizzled you were able to interrupt casters.
I know that for sure because I used this strategy a lot with my pvp dexer "weaken weaken weaken, hally autohit" that was a strong combo and only 4 mana used

I tried to look for proofs but I wasn't able to find any, maybe someone more experienced will go and snoop around.
Thanks for your attention
Have a nice day