Lunar Convocation needs to be banned from standard and alchemy
Way too strong for a 2 mana cost enchantment. The problem with this card comes down to the same idiotic design of many other cards in the current blocks.
It is way to easy to get its spawn trigger off as well which results in a game where if you don't get lucky and draw the one card in your deck that can remove it if you even have that card, the other player just sits back running combo rather than playing cards in their hand.
So they sit back with 7+ cards and a bunch of free creatures for little cost. Even worse, the life loss is negated by simply running case of the uneaten feast or another such lifegain card.
Wizards of the Coast, you need to thoroughly playtest your sets with the current standard blocks in order to find cards that make the game unfun for the other player and can guarantee a win from one player just for playing one or two cards like Lunar Convocation and a large number of other cards in the current standard. It's not fun to play against and ruins the game for the other player so it needs to be banned and in the future cards like this should not be printed.