If you kill a "Life Tool" or a "Destruction Tool", they do not get cleared from the battlefield.
Possibly related to these console errors:
cardshifter.js:7562 Uncaught TypeError: Cannot read property 'entities' of null
cardshifter.js:7453 Uncaught TypeError: Cannot read property 'ATTACK' of undefined
cardshifter.js:7453 Uncaught TypeError: Cannot read property 'HEALTH' of undefined