On-sale date from Comic Reader (Street Enterprises, 1973 series) #141, March 1977. Not a variant, the 30¢ cover price was for the majority of the print run.
This issue has variants:
X-Men [Professor X; Cyclops; Phoenix [Jean Grey]; Storm; Wolverine [Logan]; Colossus; Banshee; Nightcrawler]; Firelord (guest); Lilandra (guest; face and first name "Lilandra" revealed); John Grey (guest); Elaine Grey (guest); Misty Knight (guest); Eric the Red (name Shakari revealed; villain); Dave Cockrum (cameo); Paty Cockrum (cameo); Chris Claremont (cameo); Havok (cameo flashback); Polaris (cameo flashback)
Synopsis
Eric dupes Firelord into helping him fight the X-Men, but Jean manifests her Phoenix powers once again to counter the threat. Lilandra arrives on Earth but is captured by Eric. Xavier sends the X-Men through a space portal to rescue Lilandra.