Climactic volume marks the point where the largest number of participants act at once, typically driven by panic or by a rush to join. It accompanies capitulation lows and blow-off-top highs.
Its practical use is as a marker rather than a trigger. A climax says the move reached an emotional extreme; whether it ends there depends on what follows. The standard approach is to wait for a subsequent test on lighter volume before acting, which is exactly the wyckoff-accumulation logic.
Beware of measuring climax against a fixed threshold. What counts as extreme volume differs by instrument and by time of day, so compare against a relative measure such as relative-volume rather than a raw number.
Related: capitulation, blow-off-top, relative-volume, exhaustion-gap, volume-dry-up