Eating a bag of holding confers temporary intrinsic hunger, and eating a bag of tricks confers temporary intrinsic aggravate monster.

Monsters should be immune, or less likely, to turn to flee if you have aggravate monster. This should probably only affect monsters fleeing after being harmed in combat, rather than all forms of scaring.

The stated goal of this is so that Knights who are tired of taking caitiff penalties on fleeing monsters can give themselves aggravate monster to sidestep the penalty.

Intrinsic aggravate monster from eating dogs and cats lasts for a few thousand turns; actual cannibalism lasts many thousand turns, but neither gives it to you permanently.

When you are hit by the aggravate monsters spell at melee range, you gain intrinsic aggravate monster for a little while.

Aggravate monster from a ring (and only from that) gives pets a special behavior: as they are aggravated, they will attack enemies with no regard to their current HP or the enemy’s level, basically ignoring the checks that exist. Enemies might also attack pets of their own volition (which they don’t do under normal circumstances except in retaliation).

Aggravate monster, as well as possibly wielding Stormbringer, disables Elbereth’s protection.

Rings carried by Nazgul are all artifact rings of invisibility. They autocurse and also confer telepathy, see invisible and aggravate monster.

Trollsbane blocks intrinsic or extrinsic aggravate monster.