Dracandross said:But why opponent should take it if it seems unreasonable? Not sure what rules say but at least Id allow not to take AoO to take one later.
Ridley's Cohort said:It may have been obvious to the DM who has some inkling of the Monk's AC and knew that the Monk could have easily Tumbled and suspected that the Monk is trying to help out another AC.
But an NPC who has never fought this Monk before could easily fail to perceive one of these factors, and therefore react in a way that is suboptimal overall. If the DM roleplays the NPC correctly, this will usually (but not always) work.
Nice!Sabathius42 said:The phrase "I take the AoO" in our group now is code for "I am purposefully doing something very stupid".

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.