I think this card is interesting but it lacks something (i don't know what, though).
Maybe it's a little unpractical?
I think that it would be clearer if it worked like mitosis.
When a creature dies, the ability change in
:<creature>. For example, if a Maxwell Demon dies, Spirit Well ability become
:Maxwell Demon.
However this mechanic is a little different than yours, since it memorize the first dead creature and it will not change anymore.
But this also enables more strategic choices, and also your opponent can try to disrupt your strategy by killing a creature that you don't need.
Just my 2
.