A Shadow Blade is a specific build order for a T-spin overhang, where one places the outer part (often J/L) first, and later soft drops the inner part (often Z/S) to finish the overhang.
An example: http://fumen.zui.jp/?v110@LeA3mbD3kbE3kbH3gbB3pbAoU2ATyBUASowNE1oo2A?oC7rDFb8bDuoo2AlCaDE5oo2AKoo2AB2STASoKTASYDeD04?88AQXBAANeJwnbIwobIw4bAwNyApO98AwDc/DlN98Aw1rhE?FbkOEsSQrDFbEcEo488Aw3DXEsW98AQP88AQ5VXET/BAAPe?QpnbRpnbQp3bAwNkAh1STAS4FNEMjboEF388AQzBUASY91D?loo2Asi2rDFbUED7eBAwN5A08taEFbUfD1uMoDFbMLES3MX?EFb82Dzoo2AjiMDEF388AwnY9Az8znDvT98AQzDeDk488AS?AAAAAwNhAMo2TAySzTASIzrDloo2ABmTeEoIyTASobrEh0V?DEFBAAAhdC3gbI3gbI3gbI3gbH3hbZiQpC3ibAAYiRpB3jb?AAYiQpC3jbAAibA3rbAwNAA7eAAwNjAhF98Aw3DXEsW98AQ?S88AwBRoDFb8bDFbEBEBPVTASIzBAIdZiobYiobYi8cAwNA?AHdkzoblzobkz9cAwNcAz8znDvT98AQzDeDk488AQ51JEp9?brDkoA6A