There are seven different colors of ISO-8 in the Facebook game Marvel: Avengers Alliance. Each different color of ISO-8 comes in multiple specific types. Each type grants a hero a bonus to a specific set of stats. Yellow ISO-8 is the exact opposite of red ISO-8. These crystals only grant bonuses to defensive abilities. Defense stats, evasion and defense, are usually considered the weakest stats to improve in this game, because they do not directly help you defeat enemies and the stats are easily ignored in PvP. In PvE, though, evasion is actually one of the most useful stats in the game, especially in heroic battles. The following guide to yellow ISO-8 in Marvel: Avengers Alliance will give you all the information you need to properly equip your heroes with these ISOs.
Reactive Speedy ISO-8 (Evasion / 12,000 Silver, 3 SP) – Speedy ISO-8 increases the evasion of the hero it is attached to. As previously detailed, this doesn’t have a huge benefit in PvP, because there are too many status effects that can completely negate evasion or status effects that can simulate evasion at a cheaper opportunity cost. PvE battles are a different matter altogether. Fewer enemies ignore evasion outright for starters and heroes that can offer avoidance benefits aren’t always a good fit due to enemy classes. That makes this ISO slightly better to use. The main use for Speedy is dealing with a few specific heroic battles. There are some battles, like Phoenix vs. Selene, where getting hit even once is basically a death sentence. In these battles, load up on Speedy and simply accept that it is going to be a long battle.
Reactive Tough ISO-8 (Defense / 14,000 Silver, 3 SP) – It is strange that Tough is more expensive than Speedy, because it is much less useful. Defense is even easier to ignore than evasion in PvP and the benefits of it tend to be a lot more dubious, since it can never prevent a status effect. There is basically never a good reason to equip this ISO. If there is ever a hero where you want to increase defense, you are always better off increasing defense and health at the same time, thus using the Sturdy ISO-8 instead of Tough. If you happen to have some lying around, there is no reason not to augment a hero with unfilled slots, but you should never actually spend silver on this ISO-8.
Reactive Guardian ISO-8 (Defense, Evasion / 19,250 Silver, 4 SP) – The incredibly low cost of this ISO makes it almost worth using. Defense and evasion are rarely that useful a combination, but they actually aren’t too bad when stacked on a hero that already has high values in both stats. That is actually incredibly rare, but there are exceptions, like Captain America. In fact, WWII Captain America is actually one of the rare heroes that benefits highly from Guardian. The main flaw of this ISO is that defense is meaningless if evasion works. So, you need to see this as a chance to improve evasion with a good safety net when it fails. It is a useful choice on a few heroes with protect abilities, but most of the time you will want an ISO that increases a third stat as well.