Ah, I haven't quite addressed that myself.
After some deliberation, I've decided that anything that would destroy itself by its own effect does not affect it. Meaning deathclock mechanics, as seen on Sundial or Dimensional Shield, nor shields like Bone Wall will trigger Intervention. However, it still prevents Sacrifice and Dead or Live abilities.
Death by Acceleration | Overdrive or Poison does not affect Intervention. Also, Intervention does not save Yatagarasu from itself. If Yatagarsu were to die from a Spell, it'd be left at 0 but then it would die when it hits itself with Intervention and you, the owner, would take 3 | 5 damage.
It will protect creatures from Flooding, but only for so long. Damage will be done to the owner of Flooding | Inundation.
Note that Intervention is Passive.
Now for a question. Would this be OP if it stacked? E.g. Multiple Yatagarasu triggering for only one Deflag?
Also, how should this work in the case of spells like Lightning? Should it stop it entirely, or should some damage still be done to the target?