As Of Patch 3.17(?) This Needs To Be Done On Tier 16 Maps To Have A Chance Of Happening.
Use A Vaal Orb On Any Tier 16 Map And It Has A Chance To Turn Into A Vaal Temple Map.
- Wiki Says 1/10 Chance
- I Bought 60 Tier 16 Maps To Use For This, Only Took 5 To Pop.
- It's RNG/Luck Based So It Might Not Pop For 10's Of Maps (Some Guy Somewhere Said It Took 50 To Pop)
Achievement Pops When You Get Your Temple Map.
Good Luck!