Bloodspore Thrinax has at least two +1/+1 counters.
Cryptic Trilobite has at least one +1/+1 counter.
Steps
Activate Cryptic Trilobite by removing a +1/+1 counter from it, adding ({C} magic symbol) ({C} magic symbol) that can only be spent to activate abilites.
Repeat step 1 until Cryptic Trilobite dies as a state-base action due to having zero or less toughness.
Othelm triggers, untapping itself.
Activate Othelm by paying ({2} magic symbol) and tapping it, returning Cryptic Trilobite from your graveyard to the battlefield tapped with at least two +1/+1 counters on it.
Repeat.
Results
Infinite colorless mana that can only be spent to activate abilities.