Three types of entry / exit descriptions are available to the builder. They are:
@osucc - What OTHERS see when you leave a room to enter another.
@succ - What YOU see when you leave a room to enter another.
@odrop - What OTHERS see when you ARRIVE in a room from another.
Each is written in the same way, just from a different point of view. They always start with the name of the person moving from place to place. For example:
@osucc=<Enactor's name> turns to leave, a great burst of flame rising about %o as %s does so. With a somewhat stricken expression, %s vanished from view.
@succ=You turn to leave, a great burst of flame rising about you as you do so. Feeling somewhat stricken, you vanish into the portal.
@odrop=<Enactor's name> appears in a flash of smoke that leaves %p (his/her/its) face blackened with soot. %S (He / She / It) blinks a moment, murmurs, "That didn't go as expected!" and then moves off into the crowd.
%s = subjective pronoun: he, she, it, they. Same as subj(%#)
%o = objective pronoun: him, her, it, them. Same as obj(%#)
%p = possessive pronoun: his, her, its, their. Same as poss(%#).
%a = absolute possessive: his, hers, its, theirs. Same as aposs(%#).
Case makes a difference: %S will return He, She, It, They (capitalised, as at the start of a sentence). If you need an actual % symbol, use %% to get it.
