Source Core Rulebook pg. 531 4.0
You invest your energy in an item with the invested trait as you don it. This process requires 1 or more Interact actions, usually taking the same amount of time it takes to don the item. Once you’ve Invested the Item, you benefit from its constant magical abilities as long as you meet its other requirements (for most invested items, the only other requirement is that you must be wearing the item). This investiture lasts until you remove the item.
You can invest no more than 10 items per day. If you remove an invested item, it loses its investiture. The item still counts against your daily limit after it loses its investiture. You reset the limit during your daily preparations, at which point you Invest your Items anew. If you’re still wearing items you had invested the previous day, you can typically keep them invested on the new day, but they still count against your limit.
Source Core Rulebook pg. 532 4.0Requirements You can Activate an Item with the invested trait only if it’s invested by you. If the item requires you to Interact with it, you must be wielding it (if it’s a held item) or touching it with a free hand (if it’s another type of item).
You call forth the effect of an item by properly activating it. This is a special activity that takes a variable number of actions, as listed in the item's stat block.
Some items can be activated as a reaction or free action. In this case, you Activate the Item as a reaction or free action (as appropriate) instead of as an activity. Such cases are noted in the item's Activate entry in its stat block—for example,
“Activate [reaction] command.”
Long Activation Times Some items take minutes or hours to activate. The Activate an Item activity for these items includes a mix of the listed activation components, but it's not necessary to break down which one you're providing at a given time. You can't use other actions or reactions while activating such an item, though at the GM's discretion, you might be able to speak a few sentences. As with other activities that take a long time, these activations have the exploration trait, and you can't activate them in an encounter. If combat breaks out while you're activating one, your activation is disrupted (see the Disrupting Activations sidebar).
Activation Components Each activation entry lists any components involved in the activation after the action icons or text, such as “
[one-action] command.” The activation components, described below, add traits (listed in parentheses) and requirements to the activation. If you can't provide the components, you fail to Activate the Item.
Activation Components
An item's activate entry lists the components required to activate its abilities. Each component adds certain traits to the Activate an Item activity, and some components have special requirements. The components that appear in this book are listed below.
Command
This component is a specific utterance you must make in a loud and strong voice. Activate an Item gains the
auditory and
concentrate traits. You must be able to speak to provide this component.
Envision
This component is a specific image or phenomenon you need to imagine. Activate an Item gains the
concentrate trait.
Interact
This component works like the
Interact basic action. Activate an Item gains the
manipulate trait and requires you to use your hands, just like with any Interact action.
Cast a Spell
If an item lists “Cast a Spell” after “Activate,” the activation requires you to use the
Cast a Spell activity to Activate the Item. This happens when the item replicates a spell. You must have a spellcasting class feature to Activate an Item with this activation component. If the item can be used for a specific spell, the action icon for that spell is provided. If it's an item like a staff, which can be used for many spells, the icon is omitted, and you must refer to each spell to determine which actions you must spend to Activate the Item to cast it.
In this case, Activate an Item gains all the traits from the relevant components of the Cast a Spell activity.
Concentrate Source Core Rulebook pg. 534 4.0Requirements You have at least one magic item activation that you can sustain and you are not fatigued
Choose one magic item activation with a sustained duration you have in effect. The duration of that activation continues until the end of your next turn. Some activations may have slightly different or expanded effects if you sustain them. Sustaining an Activation for more than 10 minutes (100 rounds) ends the activation and makes you
fatigued unless the item's description states a different maximum duration (such as “up to 1 minute” or “up to 1 hour”).
If your Sustain an Activation action is disrupted, the item's effect immediately ends.