The lizard wakes up to find the land completely under his control. Satisfied with the work of it's vermin, it jumps out of the tree.
The beast cries out for its vermin, and a small pack of rodents with thick limbs and a flail for a tail come. The beast starts consuming the rodents, its getting bigger with each one it eats, as well as growing a pair of stubs near its forelimbs...
After eating the entire pack of 20 rodents, the creature stands on its hind-legs. Clumsily at first, it steps forward, and it turns his gaze towards his sides to be amazed by his new form. An extra set of arms has grown on him, these arms are an exact replica of his original arms. If anything, they seem to be muscular.
The beast lets out a blood-curling roar as it prides itself in its might... Pride? Something new came upon the beast. It felt good, it felt strong... The beast came to know Pride.
Knowing nothing may stop it, the beast continues to evolve. The barbs of the tail fall off, the glands that fed the barbs are discarded as the tip of the tail grows bigger and bigger. Shortly, the tip turns into a mace with spikes of bone protruding from it. His horns suffer an excruciating modification as they're painfully twisted to aim for the skies.
The beast sees itself and feels pride once more, not a single creature has reached this level of perfection. However, he's aware that as he stands, untrained, it's impossible to make use of his might.
Seeing that nothing under its command may suffice him, he decides to train himself with what nature gave him. It walks around the forested area. Shambling at first, it starts to pick up the pace until it can walk in perfect balance, now, he can't give chase to something just by walking. He envisions a being like him infront of him and starts to speed-up its pace to catch the imaginary being.
After alot of tumbling and falling, it seems to have gotten a hold on this "running" thing. He learned to use his tail for balance to give chase trough tight turns, and if needed, to use his arms to propel itself forward trough obstacles. To think that a few hours ago it was just a lizard crawling on the ground...
Having mastered his legs, he decides to test the strength of his arms with the trees. He simply pierces a tree with his clawed-limbs, ripping trough it. Now comes the fun part, using its four limbs, it lifts the tree off the ground and above his head, he lowers the tree down to his chest, then extends upwards again. He repeats this motion for hours, as he is lifting the tree, his muscles gradually become bigger and denser, soon enough, a single tree couldn't make it. He proceeds to rip a second tree with a limb and catches it with his second. He keeps repeating this exercise for hours, until he raises an entire tree with a single arm.
Satisfied with its work, it takes the trees to a clearing nearby and drops them for future use. He turns back to the forest and runs towards a tree, jumps and twists in mid-air with use of its muscular tail and cleanly fells a tree with his mace. He sizes up his damage, seeing how utterly ravaged the tree-trunk was, a simple conclusion was made: A weapon is stronger than the arms that follow it.