Activate Reito Lantern by paying 3, putting Threefold Thunderhulk on the bottom of your library from your graveyard.
Activate Grenzo by paying 2, putting Threefold Thunderhulk into your graveyard from the bottom of your library, and then putting it onto the battlefield.
When Threefold Thunderhulk enters the battlefield, it triggers, creating three 1/1 Gnome artifact creature tokens.
Activate Krark-Clan Ironworks three times by sacrificing Threefold Thunderhulk and two Gnomes, adding six C.
Repeat.
This elegant loop turns Grenzo, Dungeon Warden into an engine for recursive artifact armies by manipulating the bottom of your library. Grenzo's ability lets you cheat out creatures whose power matches his own, instantly pulling Threefold Thunderhulk from the library whenever it gets tucked there. Every time Threefold Thunderhulk enters the battlefield, its triggered ability floods the board with Gnome tokens proportional to its power, providing a steady stream of sacrificial fodder. Krark-Clan Ironworks then converts those Gnomes and Threefold Thunderhulk itself into a wealth of colorless mana, which in turn fuels Reito Lantern to recycle Threefold Thunderhulk right back to the bottom of the library to start the cycle anew.