Originally Posted by Panta
In general, it seems weird and dangerous to me to have non-combat spells in a macro with combat spells, but you have the right idea. You can actually stack the conditionals on Corruption and only have the spell in there once. I would also add 'nodead' in there, especially on the mouse over part, so you don't get stuck with your mouse over a dead add not being able to cast or something.
I've never fished in my entire time playing this game, so I'm not sure what the spell name for it is.
/use [@mouseover,harm,nodead][@target,harm,nodead] Corruption; 'Fishing'
You could also write it with Fishing using a modifier instead, which might be a little safer.
/use [mod] 'Fishing'
/use [@mouseover,harm,nodead] Corruption
You can add ':alt' after the 'mod' to specify a modifier (that will work with ctrl and shift as well). The empty brackets just make it act as the spell normally would outside of a macro when you don't have a mouseover. Since Fishing is on a modifier there's no reason to specify Corruption to your target in the final step anymore.