Transformers: War for Cybertron - Death of Hope/The Final Guardian

Death of Hope-
Zeta Prime is conquered, but the device Megatron believed to be the Omega Key simply activated the Key - Omega Supreme.
Megatron quickly discovers he can use the device to track Omega Supreme and races above the skies of Iacon in pursuit of his quarry.
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The Final Guardian-
The great Omega Supreme is vulnerable.
Megatron and his Decepticons must press their attack if they hope to overcome the guardian of Iacon and force him to unlock the gateway to Cybertron's core.

Omega Supreme has fallen, corrupted by the influence of Dark Energon.
Triumphant, Megatron forces the guardian to open the Omega Gate and lead the Decepticons to the core of Cybertron itself.