- Not to be confused with Eternia Crystal (NPC).
Eternia Crystals are purchased from the 酒館老闆 for 25 (pre-機械 Boss), 1 (post-機械 Boss) or 4 (post-石巨人). The 優惠卡 and 貪婪戒指 have no effect on its price. Because of the price increase, you may wish to stock up before defeating the mechanical bosses. When used in the 埃特尼亞水晶座, the 撒旦軍隊 事件 begins.
The Event lasts for varying lengths depending on game progress:
- Tier 1: 5 waves
- Tier 2 (After defeating any 機械 Boss): 7 waves
- Tier 3 (Post 石巨人): 7 waves + Boss wave (雙足翼龍)
The waves begin easy and get progressively more difficult until the final wave (wave 7 post and pre-golem) there is a boss as well as the invasion creatures. Defeating the boss finishes the wave, however.
- 126.96.36.199：Name changed from "Elder Crystal" to "Eternia Crystal".