I'm assuming you mean 'change one pillar owned by your opponent to a bone pillar'.
However, this'd be a spell, and not a permanent.
Or is this a permanent with a free active ability to change a pillar to a bone pillar?
can this target pendulums?
Either way, this should be compared to earthquake.
I do not see a viable strategy with nymph tears/antimatter, as that costs way too much quanta.