開山 Kai-Shan or mountain-opening means trail-blazing, not unlike the first Europeans settling in the Midwest and the West Coast in the US, two centuries ago. In the Chinese tradition, ancestors are often memorialized in family temples. Sometimes, a prosperous enough clan may choose to build a large temple to worship the very first ancestor, elevated to the deity status through Taoism. For example, in Penang, Malaysia, the Chen clan worships 開漳聖王 who was the first ancestor to settle in 漳州Zhang-zhou in Hokkien. The sage-kingship was an honorary title in Taoism.
Sometimes, however, the use of 開山 in the temple title deviates from the norm. An example is the Khai-San Temple located in Bukit Merah in Singapore:
Unlike Southeast Asia where Hokkinese en masse had also migrated to, in Taiwan, 開山 has retained its original meaning and 開山王 is still a true, not a Taoist, kingship title in reference to the one and only Koxinga. The only other temple that has 開山 in its name is the 開山宮Kai-Shan Palace in Tainan. It was erected by the Ming-Cheng Kingdom to honor 陳稜Chen Ling.
In 台灣通史 vol 22 (published in 1920), 連橫 wrote that, "開山宮： 在府治內新街。鄭氏時建，祀隋虎賁中郎將陳稜。乾隆五年修。而舊志以為吳真人，且謂臺多漳泉人，以其神醫，建廟獨盛。夫吳真人一醫者爾，何得當此開山之號？鄭氏之時，追溯往哲，以稜有開臺之功，故建此廟。而今又誤為開仙宮，更屬不通。" It is possible that, not realizing who Chen really was, other deities had been invited by the overseers to increase the temple attendance. A physician-deity, Dr Wu, would fit the bill well for those seeking medical miracles.
陳稜 (? - 619AD) was a general of the 隋Sui Dynasty (581-618AD). Records show that he had sailed from 潮州Tiochew to conquer 流求Liu-qiu in 610AD. Some, including the Ming-Cheng officials, argued that Liu-qiu was actually Taiwan while others thought it was Okinawa. This is still in debate even now; although this deed has already been cited by some in China as the historical evidence of Chinese ownership of Taiwan (or Ryukyu, for that matter).
Back to 開山王. Inside the Khye-Sian-Ong-Tua-Pek-Kong temple in Jelutong日落洞 in Penang檳榔嶼, these plaques, dating back to when the temple was built, are found:
Clearly a temple that honors Koxinga, the 開山王, at least in the Taiwanese definition. To our knowledge, this is also the only one in SE Asia. But who had built it, back in 1820?