UG infinite draw (Modern)

Main Combo - Wizard Class & Fathom Mage - Get Wizard Class to 3rd level as fast as possible. Then Fathom Mage and Wizard class can draw as much as you like, and give it as many +1/+1 counters

The Crazy Combo - If you can manage to get 2 Wizard Class to 3rd level and a Fathom Mage out, not only can you draw infinitely, you can also give as many +1/+1 counters to any other creature

Main Win Condition - Give Elusive Krasis as many +1/+1 counters as possible. Bioshift after the Main Combo is easiest, but Enter the Unknown and Hydras can help Evolve it.

Secondary Win Condition - Ramp a lot of mana with a couple Gyre Sage and put that on a Hydra

Ramp - Enter the Unknown can daisy chain, bringing out as many lands as you can draw, works best in early game. Gyre Sage has the best ramp, and evolving it is easy with a couple Dream Stalkers or Alchemist's Retrieval bouncing each other and other creatures. As with Elusive Krasis, you can also use Bioshift or Enter the Unknown. Kruphix keeps your mana. Even if it turns it colorless, that can still be used for Hydras.

Defensive Measures - Serum Visions will let you draw and scry to help control how much mana you're getting, and also put cards on the bottom that you won't need until late game like Hydroid Krasis and Wildwood Scourge. Bioshift can help keep your +1/+1 counters on the field in case your opponent tries to bounce your creatures. Blessed Respite is to keep you from drawing out and the occasions where your opponent deals lethal damage.