Blim does not have summoning sickness and cannot be blocked by an opponent.
You control a face-down creature whose front face is a permanent card.
Steps
Deal combat damage to an opponent using
Blim.
Blim triggers, giving control of
Karlov Watchdog to an opponent.
During the opponent's turn, activate
Altar of Dementia by sacrificing a face-down creature you control.
When the creature dies,
Yarus's second ability triggers, returning it from your graveyard to the battlefield face-down as a 2/2 creature, and then not turning it face-up due to