Tail the Suspect

Investigate. You may play an additional land this turn. (Then exile this card. You may cast the creature later from exile.)

Kellan, Inquisitive Prodigy

Flying, vigilance
Whenever Kellan attacks, destroy up to one target artifact. If you controlled that permanent, draw a card.

Kellan, Inquisitive Prodigy // Tail the Suspect

Birthright Boon

Search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.

Kellan, the Fae-Blooded

Double strike
Other creatures you control get +1/+0 for each Aura and Equipment attached to Kellan.

Kellan, the Fae-Blooded // Birthright Boon

Kellan Joins Up

When Kellan Joins Up enters, you may exile a nonland card with mana value 3 or less from your hand. If you do, it becomes plotted. (You may cast it as a sorcery on a later turn without paying its mana cost.)
Whenever a legendary creature you control enters, put a +1/+1 counter on each creature you control.

Journey On

Create X Map tokens, where X is one plus the number of opponents who control an artifact. (Then exile this card. You may cast the creature later from exile.)

Kellan, Daring Traveler

Whenever Kellan attacks, reveal the top card of your library. If it's a creature card with mana value 3 or less, put it into your hand. Otherwise, you may put it into your graveyard.

Kellan, Daring Traveler // Journey On

Kellan's Lightblades

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.)
Kellan's Lightblades deals 3 damage to target attacking or blocking creature. If this spell was bargained, destroy that creature instead.

Kellan, the Kid

Flying, lifelink
Whenever you cast a spell from anywhere other than your hand, you may cast a permanent spell with equal or lesser mana value from your hand without paying its mana cost. If you don't, you may put a land card from your hand onto the battlefield.

Kellan, Planar Trailblazer

{1}{R}: If Kellan is a Scout, it becomes a Human Faerie Detective and gains "Whenever Kellan deals combat damage to a player, exile the top card of your library. You may play that card this turn."
{2}{R}: If Kellan is a Detective, it becomes a 3/2 Human Faerie Rogue and gains double strike.