Druid talent · row 2 of Restoration, from level 15 (10 with Talented 5/5) · Physical

Natural Shapeshifter

Reduces the mana cost of all shapeshifting by 10/20/30%.

Game files · build 1.60.1.70291Read from the WoW Forever beta client, build 1.60.1.70291.

Compared with Classic

Classic tooltip

Reduces the mana cost of all shapeshifting by 10%.

What Blizzard said about Natural Shapeshifter, each line checked against the files.

Matches the files
Instantly convert 55% of Base Mana into 40 Energy. Shifting Power's cost is reduced by effects that reduce the cost of Shapeshifting.
The files Its effect grants 40 Energy (energize, value 40) for 55% of base mana, and Natural Shapeshifter's cost modifier mask (0xE0000000) covers Shifting Power's class flag (0x20000000), so shapeshift cost cuts apply. The site tooltip shows '[unknown value] Mana' because the cost is a percentage.
Shifting Power Natural Shapeshifter Development Notes, October 1
Matches the files
Natural Shapeshifter: Moved from Balance tree to the row 2 of the Restoration tree.
The files Natural Shapeshifter (16833) is Restoration row 2 in 70245; Classic had it in Balance row 2.
Natural Shapeshifter Class deep dives: Hunter and Druid

69876 Sep 16First beta build we archived. No changes in the client files since.