The ornamental design for a mask for disguise, as shown and described.
1. Mask for disguise
1.1 : Perspective
1.2 : Front
1.3 : Left
1.4 : Right
1.5 : Top
1.6 : Bottom
1.7 : Reference
The broken lines shown in the drawings illustrate portions of the mask for disguise and the broken lines showing a human figure in Fig. 1.7 represent environment. The broken lines form no part of the claimed design.