Activate Kenrith's second ability by paying ({1} magic symbol) , putting a +1/+1 counter on Cryptic Trilobite.
Activate Cryptic Trilobite's first ability by removing a +1/+1 counter from it, adding ({C} magic symbol) ({C} magic symbol) that can only be spent to activate abilities.
Repeat.
Notes
Once you have infinite mana, you may spend it on Kenrith's other abilities.
Results
Infinite lifegain triggers.
Infinite lifegain.
Infinite +1/+1 counters.
Infinite colorless mana that can only be spent to activate abilities.
Put all creature cards from all graveyards onto the battlefield under your control.
Infinite colored mana that can only be spent to activate abilities.
Infinite card draw for any number of players.
Infinite draw triggers for any number of opponents.