Activate Solarion by tapping it, doubling the number of +1/+1 counters on it.
Activate Solarion using Devoted Druid's second ability by putting a -1/-1 counter on it, untapping Solarion.
Repeat.

Infinite colored mana

Infinite +1/+1 counters on a creature

Solarion

Agatha's Soul Cauldron

Devoted Druid

Activate Solarion by tapping it, doubling the number of +1/+1 counters on it.
Activate Resourceful Defense by paying {4}{W}, moving five +1/+1 counters from Solarion onto Sage of Hours.
Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take at least one extra turn after this one.
Repeat each turn.

Combos with "Solarion"