An ice monster mutates as soon as it is in direct contact from the top or the bottom with a mutagenic tile. The double mutagen tile must always be placed over the monster. The beam radiates to the monster and the monster can mutate. The simple mutagenic tile must be placed under the monster to mutate it. The beam radiates to the monster and the monster can mutate. Note that on the simple tile, the mutagenic monster is always on the right.