How to use Cast On Gems in Path of Exile 2 – Destructoid

Using Cast On Gems successfully in Path of Exile 2 can be a very confusing task due to sure complexity of the systems surrounding them. Still, if you want to use them like a pro for some devastating effects, here’s everything you need to know about them.

What are Cast On Gems in Path of Exile 2?

Cast On Gems are Meta Gems that allow you to utilize a Cause and Effect clause to cast spells without needing to use them on your skill bar. When used well, they are extremely powerful, allowing for some absolutely insane combinations that will no doubt be a power spike. To actually use them though, you need to be aware of two additional mechanics that use them: Energy and Spirit.

Energy

Energy is a Meta-gem only resource that exists to be the sole mitigator of Cast On spellcasting. The way it works is directly tied to these gems. Most Cast On skills require Energy to actually trigger. Energy is built up by making use of the Cast On Gem’s mechanic you’re trying to use. To make use of Cast on Ignite, for example, you must first Ignite enemies enough times to reach the Energy cap. Once done, the next Ignite will trigger the spells attached to Cast On Ignite. More on this later.

Spirit

Spirit is primarily a resource for summons and buffs, and while Cast On gems are not your standard buff, they do count, and thus, make use of this resource. Like all buffs in Path of Exile 2, Cast On require a certain amount of Spirit and must be toggled on to function. When done so successfully, you will see a buff icon of the Cast On effect at the top left corner of your screen. If you don’t have enough Spirit, you cannot use a Cast On skill.

How to cast a Cast On Skill in Path of Exile 2

With the fundamentals out of the way, it’s time to actually make use of them. Before we start, the first thing you’re going to want to do is choose which Cast On you’re going to use. There are numerous types of Cast On gems you can incorporate into your build, so make sure you’re picking one that meshes well. Cast on Ignite is a solid choice if you’re playing a Fire Sorcerer, as an example.

Once you’ve selected a Cast On to use, drag it to an open slot in your Skill Page. It can be placed in any open Skill slot like any other skill.

Next, select a spell you wish to be triggered from the Cast On. Not every spell works on Cast On gems, but many do, so you have a ton of choices. You can input as many spells as you wish into the Cast On, so long as you have the space. However, this does come with a big caveat.

Slotting spells into a Cast On gem does not mean the spell is free. It will still cost the exact cost of the spell, whether you’re casting it directly or it’s being triggered by a Cast on effect. Because of this, you’ll want to be careful which spells you want to be triggered. Throwing in a costly spell like Comet may run you dry quicker than you’d think since you have no direct control over it once it is in a Cast On.

What’s more, you won’t be able to use your Cast On skill if the slots on it are not full. I’m not sure why this is the case; there is a very real chance this will change. Even, so, if you have multiple spells slotted, all of them will retain their normal cost, including Spirit, so using them all together in a Cast On may not be feasible. Much of this depends on your build, but keep this in mind.

You also need to be aware of how much Cast Time your slotted spells have collectively. The amount of energy required to invoke a Cast On effect depends on this Cast Time, with longer casts making the Cast On require more Energy to cap. It also depends on the enemies you’re attacking, as enemies have ‘Enemy Levels’ that determine Energy Build-up for Cast Ons.

Not all Cast On gems build Energy in the same way, and this is especially true for abstract ones such as Cast on Dodge (which basically requires you to Dodge Roll a lot to trigger effects).

The final step is to build the Energy necessary for your Cast On. If you’re using Cast On Shock, then you need to Shock enemies enough to trigger it. The same can be said about Cast On Ignite and so forth. Once you have enough Energy, trigger the Cast On criteria once more to invoke the spells attached to it.