UMP9 is a Stun Grenade SMG, stunning enemies on hit. 

Grenade travel time combined with ICD makes these rather slow at having an impact in battle. Adding in the fact that most newer enemies are immune to stuns and Stun Grenade SMGs do not have any other means of increasing their survivability means that UMP9 is not recommended for use.

UMP9’s Mod brings her stun length up to her 5 star counterpart’s and adds a skill 2 that adds some extra survivability/support potential to her kit. Her Mod III special equipment is a fancy EOT and not really needed for a maintank, so stopping at Mod II will be fine. Her skill 2 is a passive whose effect is determined by the state of the target. If the target dies before the stun grenade lands or is cannot be stunned, so that would be bosses and certain units, she provides a 25 HP shield and a 25% evasion buff to her column including herself. If the stun grenade is successful, she instead provides a 50% damage buff to everyone in her column including herself. This flexible support buff can have interesting applications, as well as attempts to fix the flaw of stun naders being useless against unstunnable enemies. There are a lot of great contenders for the maintank slot, but if one knows how to use her then UMP9 Mod is an additional option to invest in.

It should be noted that UMP9 Mod’s tiles and base tanking stats are still decent, albeit a little stronger due to her mod 1. As always, ARs that can use extra RoF in the first place appreciate it. Her skill 2 result is highly dependent on the type of enemy. It is a passive whose effect is determined by the state of the target. If the target dies before the stun grenade lands or is cannot be stunned, so that would be bosses and certain units, she provides a 25 HP shield and a 25% evasion buff to her column including herself. If the stun grenade is successful, she instead provides a 50% damage buff to everyone in her column including herself. To be able to get the most out of it, commanders should know which version of the skill will proc against the enemy you are facing. If directly tanking the enemy is not the concern but just bursting them down as quickly as possible, then her mod 3 special equipment might come in handy as an EOT, but otherwise it is better to just stop at mod 2. The defensive portion of her skill 2, the hp shield and evasion buff, is generally weaker for evasion tanking than other defensive skills. Because of this, while it lightens the issue, UMP9 Mod is still not well suited for fighting bosses. However, because it provides an HP shield, which is valuable for lowering chip damage and link splashing attacks, and buffs her entire column, the defensive portion can be used to further increase her survivability against the enemies that are not stunned. Additionally, it will lower the chance that the off-tank will take chip damage, which is especially helpful for direct-fire off-tank SMGs like SR-3MP. The offensive portion of UMP9 Mod’s skill 2 is a massive 50% column-wide damage buff. This can either be used to benefit the off-tank SMG’s dps or one can move UMP9 Mod to the back row while she is in her grenade throwing animation, thus providing the backline dps ARs with insane burst damage similar to Ribeyrolles. Keep in mind that doing this means risking the maintank’s protection while UMP9 Mod moves to the backline before her stun kicks in, and will not provide anything useful to the dps if the enemy her stun grenade lands on turns out to be dead or unstunnable. UMP9 Mod still suffers from certain issues due to her stun grenade’s niche applications, but with some creative applications and good skill management she can provide some great utility to a team.