Cryptic Trilobite has at least one +1/+1 counter on it.
({1} magic symbol) available.
Steps
Activate Together Forever by paying ({1} magic symbol) , targeting 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.
Cryptic Trilobite dies as a state-based action due to having zero toughness.
Together Forever triggers, returning Cryptic Trilobite from your graveyard to your hand.
Cast Cryptic Trilobite, choosing one for ({X} magic symbol) , but paying ({0} magic symbol) due to Ugin.
Repeat.
Results
Infinite colorless mana that can only be spent to activate abilities.