Felidar Guardian enters the battlefield, triggering itself and Dual Nature's first ability.
Resolve Felidar Guardian's ability, blinking a mana-producing permanent you control.
Activate that permanent by tapping it, adding at least ({1} magic symbol) .
Resolve Dual Nature's first ability, creating a token copy of Felidar Guardian.
When the token Felidar Guardian enters the battlefield, it triggers, blinking the nontoken Felidar Guardian.
When the Felidar Guardian leaves and enters the battlefield, it triggers Dual Nature's second ability, Dual Nature's first ability, and its own ability.
Resolve Dual Nature's second ability, exiling all tokens named Felidar Guardian.
Repeat from step 3 any number of times.
Once you have infinite mana, you may blink any permanents you control any number of times in step 3.
Results
Infinite blinking of permanents you control.
Infinite ETB.
Infinite LTB.
Infinite mana permanents you control that enter the battlefield untapped can produce.