Didact Echo {4}{U}
Creature — Spirit Cleric
When Didact Echo enters the battlefield, draw a card.
Descend 4 — Didact Echo has flying as long as there are four or more permanent cards in your graveyard.
The folk of the Sun Empire respect their ancestors. The Oltec go further, communing with spirits of esteemed elders after death.
3/2
For ability words, they tend to prefer to choose something that's thematic with the set, even if it means using a new one to represent a mechanic very similar to something an old ability word represented but which makes less sense to use thematically. Keep in mind that ability words have no actual rules meaning and exist entirely for flavor, usually to relate effects of different cards that are thematically similar. Descending seems to be a theme lore-wise in this set, and something like threshold or undergrowth might not have fit in quite as well.
Makes sense, I missed that this was an ability word, not a mechanic. I guess descend/descended has rules meaning in the same way that 'dies' does but given its thematic name it's not likely to be reused.