Back in the days when tribal decks ruled competitive Magic the Gathering in early 2008, Ego Erasure was a cute card to really mess up someone’s game plan. Elves, Kithkins, and Faeries were extremely powerful tribes that ruled the game for a while. With all of the Tribal support, playing this spell at instant speed could really ruin someone’s combat phase. This interruption could buy you extra time to find answers or thwarting their attempt to beat you badly enough to set them back for you to stabilize.
Of course, the one powerful tribe not already listed here was the one that stood to benefit the most. The Merfolk are still a very powerful tribe in the Modern and Legacy formats today. Of course, in 2022, they’re more powerful than ever with new cards for the tribe being printed all the time. When Lorwyn was still legal in Standard, several top decks did sideboard about three copies of Ego Erasure. These decks were primarily Faerie and Blink decks, which needed to make good use of Ego Erasure to shut down tribal effects, especially those of the often oppressive Merfolk. With opponent’s Tribal Lord stat bonuses negated, opposing creatures were just weak enough to be dealt with in simple chump blocking fashion. Another popular card that Ego Erasure countered was the Changeling creature land Mutavault, which still sees some play today.
Will we ever see Ego Erasure in a competitive sideboard again? Sure, tribal decks are still a thing, including Goblins and Merfolk. However, targeted removal has become much more powerful in the decades since Ego Erasure was printed. While this might still be a neat trick against tribal decks, there’s not really much reason to sideboard it. Sure, your opponents most likely won’t see it coming, and it could be a random blowout. This is just one of those combat trick cards that was printed during a very different era of Magic, and it probably will never see play again.
That being said, there will always be players trying to make a card work somewhere. In some rare cases, there are some “Tribal Tribal” EDH decks that will make use of Ego Erasure. In particular, Reaper King and Morophon the Boundless play as many Changelings as possible to take advantage of any and all Tribal effects. Ego Erasure can be a cute combat trick to blow out an opposing player with an alpha strike, since only one player is affected by Ego Erasure at a time. Outside of the most casual one-on-one Commander play, however, Ego Erasure is simply going to be underwhelming too much of the time to be worth running with the bevy of much more powerful Blue spells in the format.