Place it in the middle of a boss edit, after a warning sound sets up the threat and before the final impact lands. Start with the Danger Alarm Meme Sound to signal danger, let this clip carry the phase change, then finish with the Inception Horn Sound Effect as the transformed character appears.
关于此声音
This is a short 5-second excerpt of the fan-made battle theme for Sans in Undertale Last Breath Phase 2, driven by fast, escalating music that builds toward a harder fight. It feels tense, dramatic and urgent, like a final boss has become far more dangerous. The clip comes from the fan-made Undertale Last Breath AU, not the mainline Undertale soundtrack, and fans recognise it from battle recreations and meme edits.