Bob the Builder

I don't think you're on the right track here. The if statement you altered is (I'm sure you know) meant to catch usage of teleport level 1, flywing (level 1), and butterflywing (level 3). The only effect of the change you made should be that teleport level 2 will be treated like butterflywing. Teleport level 1, flywing, and butterflywing will not be processed any differently. You can read about clif_skill_nodamage here. It is not directly related to player invulnerability. Regardless, this section of code is part of a switch statement. The nested break statement there means (I believe) that after flywing, bwing, and tele 1 w/ no menu option, this case ends and the remainder is not executed. The issue must be coming from somewhere else. I'd look closely at the following files: monster.conf (I know you know; try with an unmodified copy) pc.c, and clif.c (If you made changes around 'pc_invincible_time' anywhere.) battle.c (Review all changes) You can try to narrow the issue down by swapping out one modified file for an unaltered copy at a time. If you've got any questions just let me know.