Cast Explosive Welcome by paying {7}{R}.
Holding priority, cast Reiterate with buyback by paying {4}{R}{R}, copying Explosive Welcome twice and returning Reiterate to your hand.
Resolve an Explosive Welcome copy, dealing 5 damage to any target and 3 damage to any other target, and adding {R}{R}{R}.
Repeat step 3 for the other Explosive Welcome copy.
Repeat from step 2.
NOTE: Because Explosive Welcome requires two separate targets, you may need to target yourself if you are down to one opponent and they control no other applicable targets. It is best to ensure you control creature(s) to target with the damage, or that you have a high enough life total to sustain it.

Infinite damage

Infinite magecraft triggers

Infinite storm count

Explosive Welcome

Reiterate

Twinning Staff

Cast Explosive Welcome by paying {7}{R}.
Holding priority, activate Rootha by paying {2} and returning it from the battlefield to your hand, copying Explosive Welcome.
Resolve the copy of Explosive Welcome, dealing 5 damage to any target, 3 damage to any other target and adding {R}{R}{R}.
Activate Sneak Attack by paying {R}, putting Rootha from your hand onto the battlefield.
Repeat from step 2.

Infinite ETB

Infinite LTB

Rootha, Mercurial Artist

Sneak Attack

Cast Explosive Welcome by paying {7}{R}, targeting any two targets.
Holding priority, activate Uyo by paying {2} and returning two lands to your hand from the battlefield, copying Explosive Welcome, targeting any two targets.
Resolve the copy of Explosive Welcome, adding {R}{R}{R}, dealing three damage to any target and dealing five damage to any other target.
Activate Patron of the Moon by paying {1}, putting two lands onto the battlefield tapped from your hand.
Repeat from step 2.

Infinite landfall triggers

Patron of the Moon

Uyo, Silent Prophet

Combos with "Explosive Welcome"