Thats the ability Illidan has in one of the night-elven-campaign-maps of tft.
You must bring Illidan to a signal, he changes to be green player and starts channeling to close one of the gates. While that creatures spawn. This ability is completely useless for own maps. It's only needet in that one campaign mission.
Channel is the ideal dummy spell for trigger-based spells. You can change the targeting behavior, almost all of the Art fields are valid, and it can be made into channelling or non-channelling as you see fit.
To make it non-channelling, set the Follow Through Time to 0.00.
You'd probably want Disables Other Abilities to False and Show UI to True in 99% of cases.