If an opponent creature is reduced to 0 toughness through his ETB (Enter the Battlefield) effect, they'll die, adding another +1/+1 counter to Sephiroth
I get that the Ninjutsu and saboteur effects linked to each ninja thus far makes for a limited design space and that while cool, Ninjutsu can be complex to understand when you first encounter it
Repurposing Bay could be super valuable here
Although a niche case, Death's Shadow can be paired with an enchantment, Phyrexian Unlife, to allow it to exist without its statistics being hindered
Supreme Verdict is a board wipe that, no matter how much blue mana and counterspells may appear to be in your way, will always resolve
Damning Verdict Damning Verdict feels great for a counters matter deck