Coexisting in two timestreams

You have the ability to coexist in two different timestreams: the one you exist in now, and one other of a time or place of your choice.

Caveats:

• Time continues to go forward in both worlds, even when you're in the other.
• If you die in one timestream, you exist only in the other.
• When you're gone in one timestream, you cannot be found in the other.
• You cannot make any massive historical changes-- any attempts to meet with the great thinkers of the past, invent cell phones in the 1400s, or do anything like that will be thwarted.
• You automatically know the language and the basic customs of the place you choose.