It's effective for next 4 turns. After that it become a crazy resource drainer. Not only this but you have to use your nora wisely if you want to avoid catastrophe. It needs a cut on base cost or on the drawback because Emercency Kit shoebox it so easy
Sometimes runes are just outclassed, in those cases, you can either rework them or forget about them. Why don't you want to forget about it? Tell us.
Rune should not be destroyed if you dont have the nora at the end of your turn. Other runes that cost nora per turn do not destroy the unit it's equipped on.
IMO the life or death clause attached to symbiote should remain. I like runes that grant great benefits at a great cost. In Symbiote's case I feel that it should be granting a greater benefit if there is a chance that it could instantly kill your champion should u lose your nora. Seems as if the potential sacrifice you are making to use Symbiote does not equate to the flimsy benefits the equip offers. Emergency equipment outclasses Symbiote in more ways than one. You are offered detection 3, melee specialist, and +1 speed when u are not near a font or deployment zone. Whereas Symbiote offers +1 armor, sentry 2, detection3, and melee poison rank 3. The Symbiote is a potential death trap which slowly sucks your nora away at 5 per hit. The player should be offered much better abilities if this stupid creature is gonna suck 5 nora per turn with a potential death sentence attached to it. Everyone knows speed>armor and there aren't many instances where I really need sentry because most of the time I have flyers or something else for spell presence.
Maybe try changing it to: Poisoned on melee attack TO Poison 3 scrap: 1+ armor and sentry keep everything else as is. This makes it a stealth counter and can turn a ranged unit into a nuker for the price and potential double drawback I find that to be a route that could be explored upon
Symbiote has one of the best lore texts +arts in the game. Sadly very few people seem to get the humor.