Complex sentence: The players of the 1915 championship Hamilton team, apparently as revenge for Toronto's refusal to relinquish the trophy in 1912 and 1913, added a shield for the 1908 Tigers team to give the appearance that their organization had won the first Grey Cup.
Split into simpler sentences: The players of the 1915 Hamilton team that won the title were said to have wanted revenge for Toronto's refusal to relinquish the trophy in 1912 and 1913. They added a shield for the 1908 Tigers team to give the appearance that their organization had won the first Grey Cup.