Thanos, the Last Eternal

Trample, double strike
When Thanos, the Last Eternal enters the battlefield or attacks, search your library for an Infinity Stone card and put it onto the battlefield attached to Thanos, the Last Eternal.
"With all six stones I could simply snap my fingers, and they would all cease to exist. I call that mercy. The hardest choices require the strongest will."
- Thanos to Doctor Strange