Do you mean the nuke everything skull button? I don't think the base game has any erasers, the system that the doodleordie servers use for storing the drawing images only stores lines, so the erasers that exist in the app are all that I could make while keeping the data readable by the servers.
As for the skull button, if you just want to erase the entire screen, you could add a new layer and hide or remove the one you don't want to use. The layers that aren't set to visible won't be sent to the server. There should also be a keyboard shortcut (Alt+F) for undoing everything on a layer if you want to start over, and maybe redo the first few strokes. But I didn't think it was important enough to add a button for it. edit: no wait, there is a button for it, and for undo. Sorry, I don't know what eraser you are talking about.
