Simplify the following text for a Grade 6 native English-speaking person.
Original: During this period , an alliance between Rob M , Amber ( who already had their own alliance early in the game ) , Rupert and Jenna L. would become dominate for Chapera .
Simplified: During the period where the tribes had been absorbed , an alliance between Rob M. and Amber ( who had formed their own alliance early in the game ) and Rupert and Jenna L. formed , which would stay strong until the final four .