The maximum egg capacity of a dragon during a replacement action is determined by the printed egg capacity of the new dragon card being played. Any surplus eggs beyond this printed capacity are discarded.

This rule is explicitly stated in the Guild of Highlands ability description on Page 13. When a dragon is replaced (i.e., a new dragon is played on top of an existing dragon), the original dragon becomes tucked, and all cached resources, tucked cards, and eggs associated with the original dragon transfer to the new dragon. However, the new dragon can only store eggs up to its printed capacity, and any excess eggs are discarded.

Summary

• The printed egg capacity of the new dragon determines the maximum number of eggs it can hold.
• Any eggs exceeding this capacity are discarded during the replacement action.

Source: Page 13, Guild of Highlands ability description.

Source: Wyrmspan Rulebook (pp. 13, 2, 6, 8, 9)