Slay The Spire

This guy's gimmick (Time Warp) is that it immediately ends your turn and gains Strength for every 12 cards you play. It is easier to beat with a deck that does high damage with each card, rather than spamming low-cost cards for victory. Accordingly, the Silent (usually) has the hardest time.

The Time Eater has no specifically dangerous attacks, but can inflict Weak, Vulnerable and Draw Reduction, so a stack or two of Artifact can help. Once you reduce its HP below 50%, it will heal back up to 50% and remove debuffs, so stop using cards at this point to save on stacks of Time Warp.