Support gem idea: Inner Wisdom (fixed bonus to levels)

Inner Wisdom
Tier II Support - Intelligence

Supports any skill that deals damage, granting three additional levels but preventing further level alterations.
Cost and Reservation Multiplier: 120%

+3 to Level of Supported Skills
Other modifiers to Level of Supported Skills do not apply

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It can be difficult to hybridize between archetypes due to the strength of additional gem levels incentivizing you to stick to a single archetype of skill; by providing a single stronger level supplement that does not combine with your gear, Inner Wisdom breaks down this barrier as a versatile but "capped" improvement.

In addition to global gem levels and those from the Mastery supports not applying, Inner Wisdom would also inhibit the additional level from Corrupting a skill gem.