Yeah I see the angle for the item but in reality the 100% resist for a full 8 seconds just completely nullifies a lot of heroes' and items in the game. It also acts like a parallax which I'm not sure if it's intended but basically any spell stun ability will do nothing, no stun. In terms of baiting for a team fight, 8 seconds is long enough to even if it is baited engage with because again, you have a full 8 seconds of spell immunity and nothing can stun you. I find it most annoying in the late game as a lot of heroes won't have the item before 35+ minutes into the game, so if I'm tass and I push tab, I see no Tetra, I continue to build spell dmg- 20 or so minutes later a wild tetra appears and I now do basically 0 dmg to that hero. I strongly am for a decay or at the very least some sort of trade off- like taking 100% extra physical dmg after the duration ends.