There's only one thing on the board that doesn't die on the spikes . . . and congrats for not succumbing to the walkthrough. The only way not to beat a puzzle is to check the walkthrough. Because then you can never do it yourself.
I'm also stuck on this level - I know what doesn't die on the spikes, but I have no clue how to apply that because once it's on the spikes, nothing else can interact with it (other than pushing things against it?) Help??