Plant it to grow Stalagmite. These dangerous spikes grow from the GROUND (StalaGmite!) as water drips down and accumulates minerals. Cave Dirt will blend into them seamlessly.
Stalagmite Seed price in Growtopia: sells for about 47 DL 19 WL (median of 1 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.