Speed Force
In season seven, Nash Wells sacrifices his life in order for the creation of an artificial Speed Force. As he died, the other versions of Wells inside of him said their goodbyes to Barry. However, this somehow revives the original Harrison Wells that was killed by Thawne. The original Wells, who is now able to time-travel, helps Team Flash bring back the natural Speed Force from within Iris using the Artifical Speed Force Machine. He is currently using his time-travel abilities to re-live his moments with his wife.