Grizz's Lair Key

"This key opens the door to The Grizz's private hangout. It was made from the tusk of the first and only mammoth who made fun of his fancy jumpsuit."

- In-game description

Grizz's Lair Key is a treasure found in Sly Cooper: Thieves in Time. It is worth 238 coins and gives approximately 45 seconds to be returned to the safe house before it disappears.

Description
It is a wooden key with bone, likely mammoth tusk, "cuts" held on with a leather strap. The bow is a ring made of stone. According to the description (which states that this key opens the door to the Grizz's private hangout), this may be the key that Sly stole off of the Grizz in "Unexpected Ties."

Location
Just east to the center of the map is a cave across a river that can only be crossed by using the Sabertooth Costume. Jump the river, then use the Thief Costume to Ninja Spire Jump on the switch. Slow down time and cross the river, using Ninja Spire Jumps and Rail Walks to reach the costume door.