Didn't Receive Sinister Calling

In order to get the Sinister Calling achievement:

• Both the Sinister Squashling and the Hallowed Helm must be obtained by the same character
• The Sinister Squashling can only be acquired through looting an event container or purchased through Tricky Treats to count for the achievement
  • Buying it on the auction house does not count
• The Sinister Squashling must be learned

The criteria for this achievement may be completed over multiple years. For example, you can obtain the pet one year, and the helm the next year and it will still count for the achievement.