In this talk we show how to develop a coalgebraic modal language  which is obtained from a friendly interaction of predicate liftings and Moss's nabla modality. The main technical tool for this marriage is that of presentations of functors by operations and equations. Some of the features of our language are: it is an equational language and it has a sound and complete axiomatization
for any weak pullback preserving set functor.

This is joint work with Alexander Kurz.