Infinite +1/+1 counters on certain creaturesInfinite mana creatures you control can produce except ones that attacked or entered the battlefield this turnInfinite untap of creatures you control except ones that attacked or entered the battlefield this turn
How it works
At the beginning of your end step, The Fifth Doctor triggers.
Holding priority, activate mana-producing creatures you control by tapping them, adding at least 2.
Activate Adric's first ability by paying 2 and tapping them, copying the Fifth Doctor's trigger.
Resolve the copied triggered ability, untapping all creatures you control that didn't enter or attack this turn and putting a +1/+1 counter on each them.
Repeat from 2.
This clever partnership turns your end step into an infinite loop of growth and resource generation. By using Adric, Mathematical Genius to copy The Fifth Doctor's end step trigger, you can repeatedly untap your mana-producing creatures and stack up infinite +1/+1 counters. Because Adric's copying ability only requires a modest mana investment and a tap, you can infinitely cycle the untaps and counters as long as your creatures didn't attack or enter the battlefield that turn.