Activate Soldevi Digger by paying 2, putting Orcish Bowmasters on the bottom of your library from your graveyard.
Activate Grenzo by paying 2, putting Orcish Bowmasters into your graveyard from the bottom of your library, and then putting it onto the battlefield.
When Orcish Bowmasters enters the battlefield, it triggers, dealing 1 damage to any target, then creating a 0/0 Orc Army creature token and putting a +1/+1 counter on it.
Activate Ashnod's Altar twice by sacrificing the Army and Orcish Bowmasters, adding CCCC.
Repeat.
This clever loop turns Grenzo, Dungeon Warden into a relentless engine by utilizing Soldevi Digger to continuously recycle Orcish Bowmasters from the graveyard back to the bottom of the library. Each time Grenzo brings the Bowmasters back onto the battlefield, its entry trigger lets you ping any target and amass an Orc Army token. You then feed both the Bowmasters and the freshly made token into Ashnod's Altar to generate the exact mana needed to fuel the Digger and Grenzo's ability over and over again.