Call of the Full Moon — ruling 1

Call of the Full Moon's last ability will look at the entire previous turn, even if Call of the Moon wasn't on the battlefield for some or all of that turn. For example, if you cast Call of the Full Moon and another spell on the same turn, you'll have to sacrifice Call of the Full Moon at the beginning of the upkeep of the following turn.

Call of the Full Moon — ruling 2

A single player must have cast two or more spells during the previous turn for Call of the Full Moon's last ability to trigger. If multiple players each cast just one spell during that turn, the ability won't trigger.

Call of the Full Moon : règles, fonctionnement et interactions (MTG)

Call of the Full Moon is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Enchant creature Enchanted creature gets +3/+2 and has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.) At the beginning of each upkeep, if a player cast two or more spells last turn, sacrifice this Aura.

How it works : Call of the Full Moon

Original English text — Wizards of the Coast / Scryfall

#1June 22, 2015· Wizards of the Coast
Call of the Full Moon's last ability will look at the entire previous turn, even if Call of the Moon wasn't on the battlefield for some or all of that turn. For example, if you cast Call of the Full Moon and another spell on the same turn, you'll have to sacrifice Call of the Full Moon at the beginning of the upkeep of the following turn.
No other card is named in this ruling.
#2June 22, 2015· Wizards of the Coast
A single player must have cast two or more spells during the previous turn for Call of the Full Moon's last ability to trigger. If multiple players each cast just one spell during that turn, the ability won't trigger.
No other card is named in this ruling.