I use Lotus Trap on enemy Mindsplitter at a bf. Can my Noxus Hopeful kill it if I attack with it?

To determine if your Noxus Hopeful (4 Might) can kill an enemy Mindsplitter while Lotus Trap is active, we must look at how combat damage and replacement effects function in Riftbound.

The Ruling

Yes, your Noxus Hopeful can kill the Mindsplitter if you attack with it while Lotus Trap is active, assuming the target's Might is 7.

Reasoning

1. Might vs. Damage: A unit is killed if it has damage marked on it equal to or greater than its Might (Rule 428.1.a.2, Rule 323.5.3b).
2. Lotus Trap Effect: Lotus Trap is a replacement effect that doubles all damage dealt to the chosen unit for the turn. This applies to all damage sources, including combat damage.
3. Calculation:
   • Noxus Hopeful's Might: 4.
   • Combat Damage: When your Noxus Hopeful attacks, it deals 4 damage.
   • Replacement Effect: Because Lotus Trap is active, the 4 damage is doubled to 8 damage.
4. Result: If the target unit has 7 Might, the 8 damage marked on it is lethal (8 ≥ 7). During the Combat Cleanup step, the unit will be killed.

Important Clarifications

• Lotus Trap Scope: Lotus Trap is not limited to combat damage; it doubles all damage dealt to the chosen unit for the turn. The "Combat Damage Only" limitation mentioned in FAQ #10022 applies specifically to the Tryndamere ability's condition (checking for 5+ excess damage), not to the scope of Lotus Trap's doubling effect.
• Combat Damage Step: Combat damage is dealt simultaneously after all reactions to the showdown are finished. As long as Noxus Hopeful remains on the field through the Combat Damage Step, its 8 dealt damage will successfully resolve.

Note: I could not fully verify the Might value of the Mindsplitter against the retrieved rules.