Exiling a dragon and returning it to play gets around Rivazs anti-recursion exile clause, but in Rakdos your only reliable way to take advantage of that is Conjurers Closet
You can also pay 1000 life points to destroy one target monster on the field whenever you like
Whenever you cast a black spell, put a +1/+1 counter on each legendary creature you control
There are two unusual cases where Narcomoeba's triggered is "delayed" so-to-speak letting you get additional Prized Amalgams into play before the Narcomoeba is returned to the battlefield
When Volley Veteran enters the battlefield, you get to deal damage to a creature equal to the number of Goblins you control
That is, except for my tolerance to the pains of power creep, extortionate microtransactions, and the pity systems that are, for lack of a better word, pitiful