A Scorch Mark
From A KoL Wiki

The Scorch appears in The Nearby Plains south of The Misspelled Cemetary after Fernswarthy's grave is found during the Wizard of Ego quest if a player is at Level 6 or higher. Ascended level 4 or 5 players will see A Temporal Rift leading to The Nearby Plains in the Distant Past and unascended players will see a A Small, Bright Light.
Clicking on the scorch gives the following message:
There's a small burned patch of ground here, smelling of used-up magical energy. You know that feeling you get from chewing on tinfoil? That's what it smells like.
References
- The Discworld novels often state that a highly magical atmosphere tastes like tin.