Is Tiel in Mortal Shell II?
Yes. The official Steam beta page explicitly identifies Tiel the Acolyte as a discoverable playable Shell in Mortal Shell II. This is sequel-specific confirmation, rather than an inference from the first game or promotional artwork.
What this establishes
It establishes Tiel’s presence. It does not give a numerical stat table, exact acquisition route, poison build, equipment restrictions or a beginner ranking. Read the current ability and upgrade descriptions before spending resources or choosing a build.
Beta and full game are different records
The beta listing states that unlocked Shells do not carry over as part of a full beta save. Do not assume that finding Tiel in the preview transfers that unlock into the released game. See Beta progress.
For the broader roster evidence, see All Shells. Keep your platform and version with any location or ability notes so they can be checked against the same build.