To get this achievement you need to pick up a Lihzahrd brick from the Jungle temple. There are two ways to break these bricks, the Picksaw pickaxe and the Drill Containment Unit mount.
The Picksaw is a 25% chance drop from the Golem boss, which can't be summoned until Plantera is defeated.
The Drill Containment Unit is a crafted mount that requires a lot of different bars. The required bars are:
40 Luminite Bars (The ore drops from Moonlord)
40 Chlorophyte Bars (The ore in the underground Jungle after defeating the Mechanical bosses)
40 Shroomite Bars (Crafted with Chlorophyte Bars and Glowing Mushrooms at an Autohammer)
40 Spectre Bars (Crafted with Chlorophyte Bars and Ectoplasm at an Adamantite/Titanium Forge)
40 Hellstone Bars (Crafted with Hellstone Ore and Obsidian at a Hellforge)
and 40 Meteorite Bars (Crafted from Meteorite Ore)
Take all these bars to a Mythril/Orichalcum Anvil to craft the mount.