Illyasviel is an average Backliner and CC unit with a 50% chance to Slow Red and Metal enemies for 6 seconds (provided full relevant fruit treasures) with each strike of her 2 stage multi-hit. Her other stats include 44k HP with 4 KBs, 4900 DPS at 460 range, 9 Speed, and an average 4440 cost and 2 min Cooldown. Her First Form has lower stats and is not relevant.

Illyasviel's CC against Reds and Metals is fairly consistent with a 75% chance of at least one Slow proc and decent ~65% uptime, as well as a very safe standing range for a CC unit. Her slightly above average range also gives her some decent generalist usage, allowing her to hit anti-Bahamuts like THE SLOTH and Master A. Her DPS is also about average for her range class, so it won't do anything astounding but lets her do well enough at dishing out damage when you're using her for CC anyway. Her HP and KB count keep her alive well enough during mid game and her speed is at a nice level where it lets her get to the action quickly without introducing much risk of going too far ahead.

Although her CC ability isn't bad, Illyasviel's niche is saturated with Rare and Super Rare units that often do the job just as well. For Reds, Enchantress and iCat usually are good enough while the cyclone drops are enough to stall Metal enemies. Few enemies of those traits outrange those common counters, and the ones that do are barely worth slowing. Her cost is okay for general use but can be a problem on money-tight Metal stages, where your cash is often better spent on critical hitters that can earn some money back. Finally, her long foreswing but short gap between multi-hits can mean she is often interrupted or misses the second hit and thus for various reasons fail to deliver on her potential DPS or CC uptime.

Overall, Illyasviel has passable base stats that will do ok in early-to-mid game, as well as high range CC that will give you some extra support against Reds and Metals. As you unlock stronger gacha True Forms or cyclone drops the number of situations where she stands out will quickly decline, and her general usage is completely obsoleted by the late game, but if you get her early on in your save then maybe you'll be glad for her.

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