Board Thread:General Discussion/@comment-26873653-20151212201934/@comment-679780-20151213051244

You're forgetting that Dr. Eggman is more concerned with Sonic over than Knuckles. While Dr. Eggman has successfully tricked Knuckles on multiple occasions he knows dupeing him only works so much and much rather be rid of Sonic than go through the effort of raiding Angel Island on the off chance Knuckles is absence.

Also, if Metal Sonic was sent to the island while he can concentrate on fighting Sonic, Metal Sonic will just as much have a hard time getting the Master Emerald as Sonic would, and certainly Knuckles may up security to take into account fast, blue hedgehogs. There is various of defences the island has such as traps, various places to hide the Alter such as Hidden Palace Zone and other security.

Another thing is that I believe Tikal and Chaos 0 are technically "deceased". It was in spirit that Tikal appeared to help Sonic stop Perfect Chaos and afterwards the two "passed over" once they found peace. Their apperances in future games such as Sonic Adventure 2 Battle and Sonic Runners have been non-canon.