Complete the following Devourer sections by performing the corresponding tasks:
First Devourer section
Get about 40 reds and 10 blues, then let the blues clean up the place of all the slime and let your reds attack the Devourer. When he leaves, clean up the slime with the blues by dragging them over it.
Second Devourer section
Get 15 browns and kill all the soldiers on the right. Let the browns kill the archers, then go to the far left corner from the entrance and kill the remaining archers with your browns. Return to exchange your browns for 40 reds and 10 blues, then put 20 reds (on a banner) on each of the two plateaus and wait until the Devourer leaves for the third part. Then, clean up the slime with the blues.
Last Devourer section
Get 40 reds and 10 blues, then put four groups of ten reds on the following strategic locations (on the balcony in front of the beast; down the stairs on the left side of the beast; behind the beast; on the right side of the beast). Drag around your blues to prevent the spread of the slime. Do this while standing to the right of the stairs to get to Solarius quickly when he is regurgitated by the beast to drain him with your evil presence spell.