Grimgnash

Grimgnash is the griffin featured in Grim Tales. Sylas wants a feather from him, and during the quest you need to tell the griffin a story. If you fail to please the griffin, he will hit 200 life points. He is also known to be the only griffin that a player will meet in the game.

The 22nd edition of Postbag from the Hedge features a letter to, and reply from, Grimgnash.

Postbag from the Hedge
The reply from Grimgnash in the Postbag consists of a 'story' from his mother, but in fact it hints future updates by almost a year ahead, featuring unreleased updates at that time.

In the desert the scarab waits.-Dealing with Scabaras

The institute reports a random fluctuation in rates of production.- ZMI Altar

The strong will help the weak.-Assist System

My two-er just beat a three-er!-Clan Wars (?)

Ogre men aren't very clean.-As a First Resort...

Look beneath the Plain of Mud.-Land of the Goblins

The threat from the north shall be of Mahjarrat made.-Defender of Varrock/Tale of the Muspah