In Dragon Ball Heroes Goku Ultra Instinct Omen, who showed to be very powerful, was attacked and put in danger when being attacked with some crystals. What are those crystals?
The glass shards and the crystals are created by Lagss. Lagss has the ability to heal people by enacasing them in the glass to heal them. She does this to Cumber in the manga.
The initial attack used against Goku was mainly Hearts's Gravity Burst attack which was strong enough to even restrain Jiren in DBH Episode 9. Hearts used the attack on the glass and forced it against Goku which the latter shattered. The crystals which you're referring to is just glass which was created by Laggs. We Don't have any information as to whether they are any different or have any unique special properties.