1. Attendantly, attender, attendingly, attendment, Attendress, attensity, attent, attention, attentional, attentive

2. Using available adjectives, one could potentially construct nonstandard adverbs such as attendantly, attendauntly, attendedly or Attendingly

3. Using available adjectives, one could potentially construct nonstandard adverbs such as attendantly, attendauntly, attendedly or Attendingly