Deep-Cavern Bat is an interesting card that combines a Thoughtseize effect with lifelinking and flyer abilities. This creature is a popular one in Black standard decks:
While not a must-have for Commander, I think the DCB has a compelling role in Commander decks that lack interactive colors. Black is usually very good at taking out creatures, but it struggles against non-creature permanents like enchantments. However, DCB’s effect is effective in combating this problem, as it allows you to remove any non-land while still providing a body.
What I find especially compelling is that DCB presents a potential avenue for politicking, as you can negotiate blocking with it to return the player’s card. This is especially true for the removal, as the player will want their cards back. In a Standard environment, this would never be possible.
A similar card that I would recommend, after reviewing similar cards, is Elspeth’s Nightmare. This is a removal spell, hand interaction, and graveyard removal all in one.