You can increase the power of your simpler concoctions. When you expend catalysts up to half your catalysts limit to use a concoction that deals damage, you can deal maximum damage with that concoction.
The first time you do so, you suffer no adverse effect. If you use this feature again before you finish a long rest, you take 4d6 necrotic damage for each catalyst expended, immediately after you use it. Each time you use this feature again before finishing a long rest, the necrotic damage per catalyst increases by 1d6. This damage ignores resistance and immunity.