Whenever you attack, target attacking creature gains deathtouch until end of turn. If you've completed a dungeon, that creature also gets +5/+0 and gains first strike and menace until end of turn.
Rilsa Rael takes the initiative the moment she lands, walking you through Undercity to grind value and threaten the Throne of the Dead Three payoff. You play a low-curve aggressive Dimir deck that protects the initiative, completes dungeons fast, then attacks with deathtouch evasive threats that turn any creature into a lethal first-striking menace beater. Keep pressure up to force opponents to take the initiative back so you can re-take it on your turn for extra venture triggers.
Built-in card and life advantage engine via the initiative and Undercity without needing extra cards
Deathtouch on attack makes even small creatures into pseudo-removal that trade up in combat
Once a dungeon is completed, the +5/+0 first strike menace buff makes commander damage and one-shots realistic
Dimir gives elite interaction, evasion, and tutors to find the pieces you need
The initiative is a magnet that puts a target on you and can be stolen by any combat damage
Relatively low impact if Rilsa is removed before you complete a dungeon
Vulnerable to fliers and reach blockers that out-race your ground assault
Board wipes and creature removal hit your venture/initiative enablers hard
A Rogue payoff and card-advantage engine that synergizes with evasive attackers and mill.
Add more take-the-initiative creatures (Caves of Chaos Adventurer, White Plume Adventurer is off-color, so lean on Dimir ones) and fast dungeon completers like Acererak to maximize buff turns. Tighten the curve with cheap evasive threats and strong protection (Counterspell, Swords to Plowshares is off-color, so use Cut Down, Fatal Push, and bounce) plus tutors like Vampiric Tutor to find Throne. Improve mana with fast rocks and a low average mana value so you can re-take the initiative every turn and apply relentless pressure.