Blasphemy is an intelligence-based skill gem that when linked to curses, turns them into auras with 35% mana reservation.
I consider the mechanics of Blasphemy to be very confusing because when it first came out, I made mistakes in using it myself. Blasphemy needs to be linked to the curses you want to use as auras. If linked to multiple curses,, +1 curse is needed or one of the two “Blasphemed” curses will be applied onto a target. Additionally, when linked to multiple curses, each individual curse will reserve 35% of your mana. Blasphemy works when linked with Enlighten and also works with Reduced Mana Reservation passives.
Blasphemy is a very powerful mechanic that has completely revolutionized auras in Path of Exile. Most curses are still very powerful even though they were nerfed in 2.4. You can read more about the nerf here. I will only be listing curses that are widely used on Blasphemy. You can find the full list of curses here.
This is generally not a curse you want to be Blaspheming unless you really need the Critical Strike Chance and Power Charges. Vulnerability provides more damage for physical builds and elemental curses provide more damage for elemental builds. In some COC builds it can come in handy such as Cospri’s Malice Discharge.
This curse is very powerful and use of it is widespread. The curse effectiveness nerfs in 2.4 did affect it quite a bit but it is still one of the most powerful curses today. Most builds have enough damage to sustain leech even on bosses. This is used because it allows people to run a damage support gem on their attacks instead of Life Leech.
This is one of the most powerful curses in terms of defenses. High end boss-farming builds usually have enough damage and Temporal Chains is the extra defense they need. Additionally, Temporal Chains makes Curse Effects on Enemies expire 40% slower. Assume you are playing a Blade Vortex build with 150% increased skill duration (increased duration support gem and some passives). You poison then applies for 5 seconds. With Temporal Chains, which acts like a more multiplier, your poison applies for 7 seconds. That is almost a 30% more damage increase with poison. That is huge and when poison stacks hit double digits, that means millions of damage.
Elemental Weakness/Other Elemental Curses
Elemental Weakness is the BIS damage curse for elemental builds. One exception is if you’re going Inquisitor because you already ignore critical strikes. You want to be using Elemental Weakness if you do multiple types of elemental damage or if you are playing in a party where people have multiple types of elemental damage. If playing solo-only with one type of elemental damage one of the element-specific curses are slightly better because they remove more resistances and add chance for elemental status effects.
This is another very useful defensive curse. It drastically reduces the damage you take from enemies. Once again, most high-end builds need defenses so this is an option. Usually Temporal Chains is a better option because it provides more utility but if you have the ability to run both curses, it is a very good combo. My low-life blade vortex character does this sometimes.
I consider this hands down to be the best physical damage curse for a variety of reasons. The first and most important reason is that this curse acts as a “more damage” multiplier. It says increased damage applied to enemies on the skill gem. Applied to enemies makes all the difference because that adds a whole another layer of damage stacking, like a more multiplier. Additionally, it applies 33% more damage with damage over time affects. This is BIS for all poison physical damage builds and very good for physical damage builds in general.