Zamorak brew

Zamorak brews are made by mixing torstol and jangerberries in a vial of water, giving 175 Herblore experience. It requires level 78 Herblore to make.

Zamorak brews temporarily raise Attack by 20% +2, and Strength by 12% + 2. It also temporarily lowers Defence by 10% + 2 and remaining Life Points by 10% + 20 (all numbers rounded down). The potion also restores around 10% of the player's prayer points.

This potion is frequently used in conjunction with Restore potions to raise lowered Defence. Contrary to popular belief, this cannot be used in conjunction with a Saradomin Brew to raise all four skills as they will cancel each other out.

Note that Zamorak brew cannot be used with the Lunar Magic spell Boost Potion Share.

People sometimes use this potion to lower their life points to either kill themselves and fully restore their stats, to respawn somewhere else, or to hit higher using Dharok's set effect.

With level 79 Summoning, it is possible to use Titan's constitution scrolls in order to effectively counter the negative side effects of the Zamorak Brew.

Another effective tactic is to use the brews with prayer potions, while fighting monsters that you would be praying against for long durations of time. Lowered defence and hitpoints don't matter, and the slight prayer restoration would keep one from using quite so many prayer potions.

Production costs
The data in this table is based on the Grand Exchange prices of the Vial of water, herb, and secondary ingredient(s). It is correct assuming all three items are bought off of the Grand Exchange and the resulting potion is sold afterward.

Also, for the above, you can use the Enhanced Excalibur to reboost your defence and restore 200 life points, which would negate the loss from the Zamorak Brew.