I wrote a cheatsheet for my own reference, which I think is accurate. On review, I realise that it doesn't cover opening invested items in the first place.
Design the effect to be installed, as though it were a spell. You can gain a similar spell bonus if you know the effect as a formulaic spell.
Decide how frequently the effect can be used each day:
1 use: Free
12 uses: +4 levels
2 uses: +1 level
24 uses: +5 levels
3 uses: +2 levels
50 uses: +6 levels
6 uses: +3 levels
Unlimited: +10 levels
Add these levels (if any) to the level of the effect.
Decide how the effect is activated:
By a person: Free
By the environment: +3 levels
NB: A Sun duration that triggers at sunrise and sunset does not ‘flicker’ but is permanently active
By a linked effect: +3 levels
Other modifications:
Penetration: +2 penetration per +1 level
Device maintains concentration: +5 levels (wears off at sunrise and sunset)
Restricted list of users: +3 levels
Effect expires (invested items only): increase your excess over the effect by x10 if the device lasts for a year, by x5 if the device lasts for 7 years, and by x2 if the device lasts for 70 years
Add these levels (if any) to the level of the effect.
Spend pawns = modified level / 10
Notes:
Maximum of MT x 2 pawns per season
Invested items and lesser enchantments cannot hold more vis than their size and material allows
Shape and material bonus apply; capped by MT
Similar spell bonuses if you know the spell
For invested items, get +1 to your lab total if an existing effect in the item has same Form or Technique
For a Lesser Enchantment you must be able to instill the effect in one season. Invested items must be opened with vim vis but can hold more than one effect, and do not have to instilled in one season.
For Charged Items, do not spend vis and gain one charge per 5 levels your lab total exceeds the modified effect total.
