Last year done with proposal defense for MA and presented some parts internationally, during the final stride. Mentor abandons for a better opportunity in a different country. No one in the department has the same expertise as my thesis. What do? All ready feeling doubtful as my work now is out of my thesis like after MA what do I do with it. Currently my MA is in literature.

What were you intending to do? Are you concerned about the supervision of your thesis or future career plans?
Academics do move jobs (it would be highly unreasonable to expect someone to jettison their career to supervise your MA thesis) so there are probably procedures in your department for the allocation of a new advisor. Is there a director of MA studies or similar who you could ask if this hasn't been made clear to you? Don't worry about the exact expertise match - you don't really need that for an mA thesis - just someone who can keep you on the right lines.

Get another supervisor with similar background or change to a different project completely. Or, is it possible to join your former supervisor in the new institution?