Teysa affects a creature's own "when this creature dies" triggered abilities as well as other triggered abilities that trigger when that creature dies
Tahngarth, First Mate As you certainly noted, recently the entire Weatherlight crew and key dorks in that saga are either being printed for the first time (Urza, Yawgmoth) or are getting a newer coat of usefulness in the sun (Sisay, Gerrard, Tahngarth, Greven, etc) for those that may care
The flavour text, however, talks about how deadly it is, which leads me to wonder if it was initially supposed to have an effect more similar to Deathtouch or even poison counters
Emergence Zone is one of the most important ones
A token that's a copy of Harold and Bob won't return to the battlefield from its owner's graveyard