Psionic Entity

Psionic Entity is legal in Commander, Legacy, Vintage, and Oathbreaker, but sees virtually no competitive play in any of them. In Commander, the five-mana cost and guaranteed self-destruction after a handful of activations make it hard to justify over creatures that generate value without a built-in expiration date — though blink and flicker strategies can reset the damage accumulation and squeeze more activations out of it. Legacy and Vintage have access to far more efficient interaction, so Psionic Entity doesn't register there. Oathbreaker is the one space where a repeatable two-damage ping at instant speed could theoretically matter if your signature spell keeps protecting it, but the synergy has to be intentional.