Tried to upgrade a 5* attack glyph as part of a mission and it failed 24 consecutive times. I only had 24 to try but thought that's a ridiculous amount of failures . 50.000 silver a go. Glyphs are occasionally rewards in events and tournament but if they don't upgrade you've literally won nothing. Why should you have to rely on RNG being kind to actually make the reward of a glyph worth something.