To get this achievement you need to beat the game only using one relic.

This might seem impossible at first glance, and you be right.
It is impossible without getting the ember enchantment that lets you choose one card to add at the start of the battle.


But once you get that enchantment it become trivial.

It is quite simple

Spam low cost cards, that summon a lot of troops, like ghosts, ghost archer, for the "sacrifice" (just don't kill all of them, before getting the orc)

And then when you finally get the orc in your hand
Use your commander skill
Place the orc near the enemy commander
And Win

Use this strat for the whole game.

More tips:
Try keeping your total number of cards low
Do not take any relics
Wacky works lab is op, try sticking the orc in there
You can ignore danger battles, because their only reward is the relic at the end
Do not take any relics
Tribal merchant is a great card
The whole deck has an amazing synergy with "Scrap iron forge" card
Do not take any relics

And last, but not least. do not forget to NOT TAKE ANY RELICS