Hoard Hauler is a creature and does not have summoning sickness.
An opponent cannot block Hoard Hauler and controls at least five artifacts.
Steps
Declare Hoard Hauler and Najeela, if desired, as attackers, attacking an opponent who controls five or more artifacts.
If you declared Najeela as an attacker, it triggers, creating a 1/1 Warrior creature token that is tapped and attacking.
Deal combat damage using Hoard Hauler.
Hoard Hauler triggers, creating at least five Treasure artifact tokens.
Activate five Treasures by tapping and sacrificing them, adding ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) .
Activate Najeela by paying ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) , untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.
Repeat each combat phase.
If the opponent controls eight or more artifacts, this combo nets infinite Treasure tokens.