Raised on attempt to Ractor#take if there was an uncaught exception in the Ractor. Its cause will contain the original exception, and ractor is the original ractor it was raised in.

r = Ractor.new { raise "Something weird happened" }

begin
  r.take
rescue => e
  p e             # => #<Ractor::RemoteError: thrown by remote Ractor.>
  p e.ractor == r # => true
  p e.cause       # => #<RuntimeError: Something weird happened>
end