Current version can be seen here. Before Beta 4.2 Gaster had 0 attack which made him especially susceptible to Nacarat Jester and Madjick. After Beta 4.2, like many other cards he was given an attack to make Muffet's Pet more useful, his HP was also reduced from 12 to 10. After Beta 4.3 his attack was lessened to 1. And after Beta 4.6 he was changed to give you a Gaster Blaster at the start of your turn instead of the end. Beta 5.2 saw his HP buffed back to 12 from 10. The Gaster Blaster itself has undergone many changes; initially it wasn't a spell, then after Alpha 2.2 it was changed to be one, costing 8g and dealing 8 damage it was then decreased in price to 6g in Beta 3.1 and then being increased to 7g in Beta 4.5.