You control at least one other modified creature with power one or greater.
Steps
Activate Altar of Dementia by sacrificing any other modified creature you control with power one or greater.
One with the Kami triggers, creating a number of 1/1 Spirit creature tokens equal to the sacrificed creature's power that each enter with at least two +1/+1 counters on it.
Resolve the Altar of Dementia ability, causing target player to mill cards equal to the sacrificed creature's power.