Poseidon, the ruthless

+3: create x x/x creature token giant with reach, Island walk, and trample, where x is the amount of Islands you control
+3: create x x/x black Charybdis creature tokens with Islandwalk, Deathtouch, and Menace where X is the number of swamps you control
-X: all creatures you control get +X/+X and gain trample if X is 15 or more they get trample and island walk and all lands are Islands