Uro, Titan of Nature's Wrath | Deadeye Navigator | Izzet Boilerworks (and one other card)

Cards

({1} magic symbol) ({G} magic symbol) ({U} magic symbol) plus enough mana to pay for commander tax, if applicable available.

Cast
Uro by paying ({1} magic symbol) ({G} magic symbol) ({U} magic symbol) .
When
Uro enters the battlefield, its first and second abilities trigger, as well as
Deadeye Navigator's soulbond ability.
Resolve the
Deadeye Navigator trigger, pairing it and
Uro.
Resolve the second
Uro trigger, causing you to draw a card, gain 3 life, and put
Izzet Boilerworks from your hand onto the battlefield.
When
Izzet Boilerworks enters untapped due to
Horizon Explorer, it triggers.
Holding priority, activate
Izzet Boilerworks by tapping it, adding ({U} magic symbol) ({R} magic symbol) .
Resolve the
Izzet Boilerworks trigger, returning it from the battlefield to your hand.
Activate
Uro by paying ({1} magic symbol) ({U} magic symbol) , blinking it.
Repeat from step 2.

This combo has been estimated to be Exhibition (Bracket 1+).