Just play intelligently- IF it makes sense for your character to do so.
And ANY martial magic with nonstandard elemental properties that can in some way provide mana regen is on par with a slayer. Slaying isn't all-powerful, just top of the line. Anything can be top of the line if you design it thoroughly.
So you want a slayer of slayer magic? Make an Anti-Elemental magic that destroys specific elements. Anti-Water magic to destroy that lake, Anti-Light magic to shroud the land with darkness, Anti-Fire magic to stifle fires and prevent their manifestation.
Just use your head and be creative. Don't just ask for a slayer of slayer magic, you don't need someone to paint it out for you.
And ANY martial magic with nonstandard elemental properties that can in some way provide mana regen is on par with a slayer. Slaying isn't all-powerful, just top of the line. Anything can be top of the line if you design it thoroughly.
So you want a slayer of slayer magic? Make an Anti-Elemental magic that destroys specific elements. Anti-Water magic to destroy that lake, Anti-Light magic to shroud the land with darkness, Anti-Fire magic to stifle fires and prevent their manifestation.
Just use your head and be creative. Don't just ask for a slayer of slayer magic, you don't need someone to paint it out for you.