"a dour, self-sacrificing life"
"a forbidding scowl"
"a grim man loving duty more than humanity"
"undoubtedly the grimmest part of him was his iron claw"
"a baleful look"
"forbidding thunderclouds"
"his tone became menacing"
"ominous rumblings of discontent"
"sinister storm clouds"
"a sinister smile"
"his threatening behavior"
"ugly black clouds"
"the situation became ugly"