A ring with a black diamond and brown stripes. Let the druid reach forward and borrow wildshape power and bring it to the present becoming a Tyrannosaurus-Rex for 30 minutes. After this, you have one level of exhaustion and have used up your wildshape ability for the near future. You recover from exhaustion on the next long rest and roll 1d6 to recover your wildshape ability on a 5 or 6, if that doesn't work on the next long rest you roll again and need a 3 - 6, on the 3rd long rest it's 100% to recover. 

When the wildshape ends, the target can't move or take actions until after its next turn, as a wave of lethargy sweeps over it.

Notes: Attune on long rest