Each unit with Corrupted also has a SummonSummon: Does something when played. ability. When the unit dies, a related "Shade"token unit is played. From Eternal's in-game glossary:
When a unit with Corrupted dies, a 0 strength Nightmare Shade is played in its place. Shades have the ability to sacrifice themselves by paying their corrupted cost to play the starting unit's Summon ability. Shades lose 1 health at the end of each of your turns.