[Antique]

Looks like a page of rule is missing: p154 sums up what it can be used for.
But the rules to do it are not there.
Unless they are hidden somewhere else?
Also reagents cant be used in spell casting, really?

[Xenon]

Reagents are used for creating a magical lodge (and temporary lodges)
For increasing the 2 meter AoE of your boosted defense
Reducing drain during rituals and preparations
Gaining an edge while summoning or banishing a spirit
Used when creating a focus


They are detected with detect magic, can't pass through mana barriers and can be recharged when recycling a focus.

[Antique]

Yeah, but how many drams of reagent am I supposed to use for each of these?

[Michael Chandra]

Wasn't Reagents in Spellcasting a limit-mod only in 5e, and in 4e all they helped you do was craft and certain rituals? So not that surprised they don't do anything for normal spellcasting now, since limits are gone.

Boosted Defense: "1 meter per dram of reagents spent", so own choice. (p143)
Rituals: "Must expend the amount of reagents specified for the ritual", & "For every dram of pure reagents spent (after the initial offering)" (p143), initial offering is nowhere described so I guess the base rituals in core don't require reagents?
Summoning/banishing: "spend reagents equal to the Force" (p147)
Preparations: "by the number of drams employed", so own choice, max 2 (p150)
Creating a focus: "The amount you need to spend" (p152)
Temporary Lodge: "by spending a number of drams of reagents equal to" (p153)