From Roll20 Wiki
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!power [--<tag>|<content> [--<tag>|<content> [...]]]
Formally:
S
→ !power tag-list
tag-list
→ ε
tag-list
→ tag
tag-list
tag
→ --tag-name
tag-indent
|tag-content
tag-name
→ emote
tag-name
→ name
tag-name
→ usage
tag-name
→ action
tag-name
→ attackcount
tag-name
→ defense
tag-name
→ damagecount
tag-name
→ txcolor
tag-name
→ bgcolor
tag-name
→ leftsub
tag-name
→ rightsub
tag-name
→ ddn
tag-name
→ desc
tag-name
→ crit
tag-name
→ lb
tag-name
→ format
tag-name
→ title
tag-name
→ multirollcount
tag-name
→ whisper
tag-name
→ string
tag-indent
→ ε
tag-indent
→ ^count
tag-content
→ ε
tag-content
→ string
count
→ ε
count
→ integer